Amnesty was the act of a government formally restoring those convicted or suspected of crimes to the status of innocent people. More than merely forgiving past criminal acts, such an action essentially wiped away criminal records, as if they had not existed.
In 2366, Sovereign Marouk proposed giving amnesty to the Gatherers as a means of allowing their return to Acamar III after decades of exile. A Gatherer leader, Chorgan, was initially skeptical of such an offer. (TNG: "The Vengeance Factor")
In 2369 the Ministers' Court of the Bajoran Provisional Government was prepared to grant amnesty to former members of the Kohn-Ma terrorist group. This included Tahna Los, who had been fleeing Cardassian pursuit and expressed a desire to return to and help rebuild Bajor. This desire was, however, merely a ruse to gain access to a runabout and attempt to destroy the Bajoran wormhole. (DS9: "Past Prologue")