(written from a Production point of view)
Described by reference author Joel Engel as Gene Roddenberry's "point man and proxy", Leonard Murray Maizlish (7 February 1932 – 7 September 1994; age 62) had been the life-long attorney of Gene Roddenberry. Though Maizlish had been a lurking background presence throughout the entire Star Trek production history, he fully emerged into the open when Roddenberry, upon being contracted for The Next Generation, brought him along to serve "on staff" and was given his own personal office on the studio lot in early 1987, even though he had no official production function or any formal say in the production whatsoever. Roddenberry, still smarting over the fact that he had been removed by the studio from creative control over the Star Trek films five years earlier, was determined to not let this happen again, and reasoned that he had a better chance of accomplishing this if he had his attorney at hand at all times during the production. (Gene Roddenberry: The Myth and the Man Behind Star Trek, p. 238) "Leonard was carrying the "Wrath of Gene" for all these years," John Pike further clarified in the documentary Chaos on the Bridge, "because Gene felt he had gotten screwed on the Original Series," which, actually, had not been entirely unjustified. This time around however, and much to the chagrin of the studio (as evidenced by Pike's above-quoted remark), Maizlish managed to hammer out a very advantageous deal for his client.
While the subsequent events were discussed in detail in Chaos on the Bridge, it was David Gerrold who had already for nearly a decade vocally recounted the events in numerous publications and at several Star Trek conventions, in no uncertain terms, be they in writing and/or speech. Summarizing, Gerrold had explained, "Gene's lawyer (Leonard Maizlish) was making it impossible for anybody to do any real work. He was rewriting scripts. He was committing (Writers) Guild (of America) violations. People were very unhappy. It was one of the worst working environments I'd ever been in. So when my contract came up for renewal, I asked Gene not to [renew it]."  Elaborating that Maizlish went even as far as surreptitiously rifling through the desks of writers in search of scripts he could illegally redact (Rick Berman, well acquainted with Roddenberry's handwriting, has recalled, "Leonard Maizlish, Gene's lawyer, would hand me a script saying these were Gene notes. I'm pretty sure they were Leonard's notes." ), Gerrold has labeled Maizlish a "(...) scumbag of a Human being. I cannot say enough things – he was a truly evil Human being."  Maizlish was at the start of the second season banned from the the studio lot, but he sneaked back in the evenings to continue his illicit practices.
Being for nearly a decade virtually the sole, highly critical voice on these events, has made some of the more purist elements of Star Trek fandom skeptical of Gerrold's sincerity on several internet blogs, among others that of TrekMovie.com and TrekBBS.com, interpreting these as being personally motivated, some of them even confusing them with Gerrold harboring resentment against Roddenberry himself. Gerrold had indeed had some issues with Roddenberry, stemming from the Original Series days, but these had since then long been resolved. But they were right in their assessment that there was also a personal element involved, which stemmed from Gerrold's script-draft for the ultimately unrealized episode "Blood and Fire", an allegory on AIDS, featuring gay characters. Much to the dismay of the gay community, Star Trek had until then shied away from gay issues (in all honesty, mirroring the prevalent attitude towards gay issues in American society at the time),  something Gerrold tended to redress with this episode, with the implicit backing of Roddenberry according to Gerrold, "So now Gene and I appeared at a Star Trek convention in November of 1986 and somebody asked "will there be gay people aboard the Enterprise?" And Gene – to give him credit for knowing the right thing to say at the right time – said "yes, it is time, we should show gay people on board the Enterprise." This got a lot of applause." Yet, Roddenberry backtracked on his promise, likely persuaded to do so by the studio in the arguable guise of "raging homophobe" Rick Berman, as per Gerrold.  Roddenberry however, had a well-known character flaw of being absolutely unable to be the bearer of bad news and dispatched Maizlish to deliver the decision to Gerrold. This Maizlish did in a particularly vulgar manner, as recounted by Gerrold, "The last time I saw [Maizlish] I was helping Herb Wright [remark: who had tried to tone down the script into the equally unrealized "Blood and Ice" variant, under strict instructions from Maizlish not to let Gerrold work on the script, only to become another victim of Maizlish] pack up his office. The lawyer came to make sure we weren't stealing anything. To my face, he called me "an AIDS-infected cocksucker. A fucking faggot"." (; Gene Roddenberry: The Myth and the Man Behind Star Trek, p. 249)
It was not the only time that Maizlish spoke in harsh terms to or of Gerrold, and the latter, shortly after he had left the production, decided to fight fire with fire by seeking out legal counsel of his own, "Later, I found out that Maizlish was telling people what a troublemaker I was, that I'd been fired because I was mentally ill, that I never did anything useful for the show – real character assassination of the worst sort. So my lawyer called him up and said, "You keep talking and we're going to own your car, your house, your dog, etc.", and that shut him up real fast. Maizlish was a disgraceful man. Fortunately, my lawyer was a Hollywood heavyweight, and when he said, "Hmmm," that was a very expensive "Hmmm," especially to the target."  Maizlish's remarks to and of Gerrold were indicative of a very boorish nature, which was to an extent corroborated by author Engel, when describing Maizlish's presence on the production, "[Maizlish had] become Roddenberry's point man and proxy, often writing memos on scripts and outlines, and sitting in on most story meetings, often without Roddenberry. He once fell asleep during a casting session, snoring loudly as an actress auditioned for her part. Sometimes he attempted to rewrite scripts. He worked on Michael Michaelian's "Too Short a Season", Roddenberry admitted to [Robert] Lewin [remark: who incidentally, was hired by Maizlish personally without studio consent, as Hurley was – which however, backfired, as Roddenberry himself was to clash violently with Hurley later on – and both promoted by him above the Original Series writing staff], "just to help my thinking on it." Inasmuch as Maizlish was a lawyer, not a writer or producer – or even on staff in any official capacity – this was a contravention of Writers Guild rules." (Gene Roddenberry: The Myth and the Man Behind Star Trek, p. 238)
The uncouth act of falling asleep during a casting session was as a matter of fact witnessed by Producer Robert Justman, and marked the only time that he actually had words with Roddenberry, with whom he had otherwise a warm and close personal relationship, hastening his decision to leave the production, "One day, I drove over to his house after Leonard Maizlish fell asleep in the middle of a casting session, right in full view of the actor who was reading for us. I was furious, and stopped the casting session, jumped in my car and rode over to Gene's house and screamed at him. It wasn't long after that I decided, "Wait a second, I can't let this happen!" I knew the show was going to be successful, it was a terrific show, but I was lucky that I didn't have to remain at work there. I gave away a lot of money by not coming back, but I think I also kept some hold of what little sanity remains to me, and physically, it was my salvation. I just decided to be happier and have less." (Star Trek Magazine Special 2014, p. 20)
Yet, what many Gerrold detractors had overlooked however, was that Justman himself had already confirmed Maizlish's detrimental influence to a large extent previously, in his 1996 reference book Inside Star Trek: The Real Story, having called his creative meddling "destructive" and also being the prime responsible agent for the earliest departure of one of the most important production staffers, Post-production Producer Edward K. Milkis, which however, opened up the way for Rick Berman and, more specifically, Peter Lauritson. (1997, pp. 433-434) Just prior to the publication of the book Justman had already delved in somewhat more detail in a magazine interview,
"Well, Maizlish made my life hell. My deal was for a year with a year's pick-up. but by the time I was halfway through the first season. I knew I didn't want to do a second season. I spent half my days being angry at Gene's lawyer. I felt I could have stayed, but with him riding shotgun, filling in for Gene, or so he thought. I felt that I didn't need that kind of grief. He was getting in my way and causing me big problems. My blood pressure rose suddenly – I've always had a great heart – and I decided I didn't want to do it anymore.
"So, well before the end of the season, I had my agent go up and say, "Hey, let him out [of his contract]." I made the offer where I would finish the season's last eight shows on more of a consultant basis, where I would just do the casting and story and editing. And all the other stuff would be left to someone else – Rick Berman and David Livingston. And I voluntarily took a cut in pay, half of what I was making. We finished out the season, the last eight shows, I finished my editing chores on them and that was it.
"(...) By that time, David was gone from the show, as was Dorothy, and they were very angry. I don't know what the heck went on between David and Gene and Dorothy and Gene, but it was evidently something. Other people had since come and gone, too. What was going on? I don't know. All I know is there was a lot of backbiting and crazy politicking going on over there; but very little of it touched me.
"Long before I left the show, Leonard Maizlish came to me and said, "I want you to know, Bob" – this is practically an exact quote – "that Gene and I appreciate all you've done creatively for Star Trek: The Next Generation, and we're going to see to it that you get a small piece of the show." I said, "Oh, great!" And he said, "However, it'll have to wait until Eileen Roddenberry's lawsuit [regarding how much eventual Trek profit was owed to her under the couple's divorce] is over, to see exactly what the piece would be." Well, as far as I know, the lawsuit is still continuing, Maizlish died some years after that and I'm still waiting for that piece. Know what? I don't think I'm going to get it!" (Starlog, issue 228, pp. 58-59)
Staunch Roddenberry supporter Dorothy Fontana had remained silent throughout the years, on what exactly transpired during this period in time, until Chaos on the Bridge, in which she revealed that she caught Maizlish red-handed one evening in the act of rifling through her office. "Nobody liked him", she stated, immediately adding, "In particular, I didn't like him." Richard Arnold added on the same occasion, "I think he thought he was speaking with Gene's voice, but I think Gene never heard the way he spoke to other people. Gene had these wonderful relationships with people who worked with him on the Original Series, like Dorothy Fontana, and Leonard was horrible to Dorothy." Whether or not Maizlish had his ailing client's interests truly at heart, by over-zealously playing upon his client's increasing paranoia of being removed from creative control, he had done him a great disfavor as the departure of the Original Series veterans had a profound effect on Roddenberry according to Gerrold, "Gene was crying because all of his friends were gone. It was because Maizlish chased them away." It confirmed Arnold's assessment that the most vicious clashes had been with Maizlish, not with Roddenberry in person.  Considering the deep emotional attachment Roddenberry had for his Original Series friends, who were the very first staffers he had brought in to form the original production nucleus for The Next Generation in October 1986, has made Maizlish's attitude towards Gerrold, Fontana, Justman, and Milkis all the more inexplicable. The now isolated and friendless Roddenberry was subsequently left dangerously exposed to studio politics at which he was notoriously inept. Maizlish was, after another series of clashes with the subsequent writing staff, definitively removed from the production at the end of the second season, as Roddenberry was from creative control due to his failing health. "Gene didn't like Rick [Berman], at all. But Rick was installed on the show by the studio as a way to keep a control on the show...to keep the budgets in line, make sure that the scripts were done. Ultimately, Berman ended up in control rather than Maizlish because Berman played the politics of the studio more effectively," Gerrold concluded. 
It was not only the Next Generation staff Maizlish managed to antagonize to no end, even movie director Nicholas Meyer had his blood pressure raised by Maizlish when he was summoned to a meeting with Roddenberry over perceived racism exhibited in Star Trek VI: The Undiscovered Country (even though Roddenberry still had no creative say in that movie as well, and which went into pre-production during The Next Generation's third season) in regard to the Klingons. A very charged, as Meyer was by no means a man to be outdone by the likes of Maizlish, meeting followed, which Meyer in later years came to regret, "His guys were lined up on one side of the room, and my guys were lined up on the other side of the room, and this was not a meeting in which I felt I'd behaved very well, very diplomatically. I came out of it feeling not very good, and I've not felt good about it ever since. He was not well [remark: an ailing Roddenberry would indeed pass away only a short time later], and maybe there were more tactful ways of dealing with it, because at the end of the day, I was going to go out and make the movie. I didn't have to take him on. Not my finest hour." 
On 22 October 1991, Roddenberry was present at the avant-premiere screening of the nearly finished The Undiscovered Country movie, giving the assembly a thumbs up when he was wheeled back to his office. True to form, once there he immediately instructed Maizlish to start legal actions against Leonard Nimoy and Nicholas Meyer at once, to have fifteen minutes of the more militaristic aspects cut from the movie. Two days later, his client was dead, and the Star Trek production staff were spared being reintroduced to Maizlish' antics, whom they only two years earlier had managed to boot out. (Star Trek Movie Memories, 1995, p. 394)
Still, for all the vilification, it was not entirely all bad, what Maizlish had brought to the table. Rick Berman has credited him with suggesting actor John de Lancie for the part of Q, who went on to become one of the most popular recurrent characters on The Next Generation, in no small measure due to the way de Lancie portrayed his character. (Star Trek: The Next Generation Companion, 2003, p. 25) Concurrently, it was Maizlish who convinced Roddenberry to keep the name Data, as was begrudgingly conceded by Gerrold, and who himself had opposed the name.  And even his illegitimate hiring of Maurice Hurley, the detrimental effect it had on Roddenberry notwithstanding, eventually resulted in the acclaimed episode "Q Who", introducing the hugely popular villains, the Borg.
Loathed, reviled and universally held responsible for the departure of all Original Series veterans, Chaos on the Bridge marked the first time that both Justman's and Gerrold's accounts of Maizlish's machinations were corroborated by a wider range of former The Next Generation production staffers, ranging from studio executive, through producers, to writing staff.
Hailing from the East Coast, Leonard Maizlish started his life-long association with Gene Roddenberry when the latter incorporated his production company Norway Corporation, Inc. on 13 February 1959,  through which Roddenberry from here on end handled his business dealings with the motion picture industry. Maizlish was hired to look after the legal aspects of Roddenberry's dealings and his presence was already felt during the production of the Original Series, as Roddenberry habitually forwarded a copy of internal studio memos to him, when communicating with the upper echelons of the studio and/or network. (Inside Star Trek: The Real Story; Star Trek Phase II: The Lost Series)
Actually, the first recorded "victim" of Roddenberry's and Maizlish's legal machinations, fell already during the production of the second season of the series. Finding himself on the receiving end was series' theme composer Alexander "Sandy" Courage. As related by Herb Solow, "When Sandy Courage was given his contract to write the Star Trek music, he was unaware of a two-sentence clause toward the end of the agreement. Thinking it was more of the usual boilerplate, Sandy signed the agreement without reading it fully. The clause, inserted by Gene's attorney, Leonard Maizlish, gave Gene the right to write lyrics to Courage's theme [remark: which he did, but which have never been featured for the very simple reason that they were bad, as Roddenberry had no musical skills whatsoever]. Almost two years later, after NBC put Star Trek on its schedule, Sandy received a call from Leonard Maizlish: "Listen, from now on we will be collecting one-half of your royalties." Sandy, confused as to how this could happen, spoke to Desilu Music Department head Wilbur Hatch and Desilu attorney Ed Perlstein. "They told me there was nothing that could be done, legally," said Sandy, and when he questioned Roddenberry, Gene explained, "Hey, I have to get some money somewhere. I'm sure not going to get it out of the profits of Star Trek."" A livid Courage left the production immediately, never to return save for two third season episode scores as a courtesy to Justman. In his twilight years however, Courage, mellowed over the years, has put the blame squarely on Maizlish's shoulders, "There wasn't any rift, really, with Gene. What happened with Gene was a I got a phone call once...it was Gene's lawyer, [Leonard] Maizlish. He said, "I'm calling you to tell you that since you signed a piece of paper back there saying that if Gene ever wrote a lyric to your theme that he would split your royalties on the theme." Gene and I weren’t enemies in any sort of way. It was just one of those things...I think it was Maizlish, probably, who put him up to doing it that way, and it's a shame, because actually if he'd written a decent lyric we could have both made more money." 
The duo had concurrently tried to do something similar with Leonard Nimoy's first vinyl album recording, Mr. Spock's Music From Outer Space, which marked the beginning of the descent into animosity of the relationship, which had started amicably enough at the beginning of the series, between Roddenberry and Nimoy. (Inside Star Trek: The Real Story, 1997, p. 185) Nimoy however, retaliated in 1991, when he torpedoed the publication of the reference book Star Trek: The First 25 Years and for which Roddenberry was to receive a co-author credit. Fully aware that his legal consent – which Nimoy had only secured in March 1978 after a long and bitter fight with Paramount Pictures and Roddenberry himself (see: Star Trek: The Motion Picture production history) – was needed for the celebratory book, he was purposely late in signing off on photos of him in the book, and subsequently wanted editorial changes made to the text of the book. A closed-doors meeting was held with Roddenberry, Maizlish, Nimoy and his attorney, but excluded co-author Susan Sackett, who was afterwards informed by Maizlish "that the book was on hold because Leonard Nimoy didn't think the prose 'lofty enough,' as Maizlish had put it, and wanted it more in the style of someone like Bill Moyers." Nimoy was far from being of a mind to further contribute to what former Desilu executive Herb Solow had dubbed "The Roddenberry Myth", or his coffers for that matter. (Inside Trek: My Secret Life with Star Trek Creator Gene Roddenberry, p. 181) Nimoy had actually waited for the latest possible moment in time to torpedo the book, as it was already geared for general dissemination.
Being typified as a "scumbag" by Gerrold was not entirely unfounded, as Maizlish was already in 1964 under investigation by the Securities And Exchange Commission (SEC) for "(...) filing contained material misrepresentations and omissions which he reasonably should have known were false and misleading concerning interim loans and losses affecting the financial condition of the company [remark: Casa Electronics Corporation] and the use of proceeds from the public offering." Sensing the writings on the wall, Maizlish recused himself on 23 November 1964, effectively disbarring himself from litigating before the SEC, in order to avoid legal punitive measures.  Nevertheless, he was readmitted to litigate before the SEC on 10 June 1965. 
Maizlish played an equally dubious legal role when he agreed in 1967 to become party to the deception surrounding the foundation of Lincoln Enterprises, the Star Trek memorabilia sales company of Roddenberry and his soon-to-be wife Majel Barrett. Roddenberry wanted to hide his legal footprints in order to obscure the questionable origins of some of his early production-used Star Trek merchandise, as well as to hide the proceeds from these sales from his then still-wife, Eileen. By transferring legal title to his attorney (who, when legally registering the company, had somehow managed to antedate the company's establishing date to 6 April 1962 – hence Barrett's below-mentioned "has been in existence for probably almost a hundred years" remark – , in the process also changing the original, short-lived company name "Star Trek Enterprises" into the new one ), Roddenberry had thrown up a smokescreen if the studio ever decided to pursue the matter legally, which however, they never did. Barrett-Roddenberry herself had actually admitted to this state of affairs, albeit somewhat circumferentially, when she later elaborated in a 1993, with contradictory half-truths interlaced, interview, "Lincoln has been in existence for probably almost a hundred years. It was originally Lincoln Publishing and it was owned by another gentleman many, many years before. His attorney was Leonard Maislich [sic.]. For some reason or another he gave the incorporation to Leonard. I don't know how it basically happened, but it really belonged to Leonard Maislich until he gave it to me in the early eighties. It [Lincoln] was merely set up for Gene to handle fan mail for Star Trek." (Strange New Worlds magazine, issue 10, Oct/Nov 1993) Unsurprisingly perhaps, and not entirely unjustified as the original Roddenberry couple was still legally married at the time of the incorporation of Lincoln Enterprises, Eileen found out later, and sued all involved parties for damages, resulting in that Maizlish was this time actually found guilty of "conspiracy to commit fraud" for his part in the deception, though it assessed no punitive damages against him. Incidentally, an unintended victim of Maizlish became Roddenberry's life-long accountant Mort Kessler, who had not been involved with the original deception, as he only became much later employed as such by Roddenberry. However, he became implicated when he in good faith attached his name to the obligatory registration renewals, and he therefore decided to settle out-of-court with Eileen.  It was for this reason that Maizlish has sometimes been referred to as Roddenberry's "business partner" in various reference works, among others by Justman in his book, Inside Star Trek: The Real Story.
After the Original Series had been canceled, Maizlish became the legal keeper of "The Roddenberry Myth", which his client had began to spin around his person, already during the third season of the Original Series and as observed by Herb Solow. To this end, every single piece of copy or film, dealing with Roddenberry and intended for publication be it in print – such as the above-mentioned Star Trek: The First 25 Years – or on film, had to go through Maizlish's office (located at 9255 W Sunset Blvd Los Angeles and heading a staff of two at the time ), to be signed off on by him personally. These even included, the pieces written or edited by Roddenberry's personal assistant, the aforementioned Susan Sackett, who had faithfully and unwaveringly stood by her employer for decades.  And indeed, it turned out that dealing with Maizlish had been a heavy burden for Sackett as well, as she has related in her 2002 book, Inside Trek: My Secret Life with Star Trek Creator Gene Roddenberry, having called him an "unsavory character" in Chaos on the Bridge.
As already touched upon by Robert Justman above, Maizlish had, aside from having presided over all Roddenberry's studio contract negotiations, also represented him during his original, bitter divorce proceedings from his first wife, Eileen, as well as all the subsequent, incessant alimony hearings which harassed Roddenberry until his dying day. 
Shortly after Roddenberry's death, Maizlish himself was struck with physical infirmity, and he survived his most famous client by only three years. (Inside Star Trek: The Real Story, 1997, p. 442)