The Jankata Accord was an accord that essentially stated that "no species shall enter another quadrant for the purpose of territorial expansion." This accord was signed by the Federation and the Cardassian Union.
Seven of Nine accused the Federation and the Cardassians of breaking the accord in 2376, but she was being overly paranoid as a result of new modifications she had recently made to her alcove. (VOY: "The Voyager Conspiracy")