Retroactive Continuity (Retcon) in the Law
The first reference to the term "retcon" in a Westlaw-accessible court opinion.
From Judge Thomas M. Hardiman's panel opinion in Northeastern Pennsylvania Freethought Society v. County of Lackawanna Transit System (3d Cir. Sept. 17, 2019):
In Lehman v. City of Shaker Heights (1974), the Supreme Court upheld a prohibition on political advertisements in buses' "car card" interior advertising spaces…. Lehman predates modern public forum analysis but has been retconned into that framework. See Int'l Soc'y for Krishna Consciousness, Inc. v. Lee (1992); Cornelius v. NAACP Legal Def. & Ed. Fund (1985).
Retcon is a shortened form of retroactive continuity, and refers to a literary device in which the form or content of a previously established narrative is changed. Retcons are often encountered in serial formats such as comic books or television series, where they serve as a means of allowing the work's creators to create a parallel universe, reintroduce a character, or explore plot lines that would otherwise be in conflict with the work. Essentially, a retcon allows an author to have his or her cake and eat it too, as it enables the return of dead characters, the revision of unpopular elements of a work, and a general disregard for reality….
If retcon manages to stick in the English language it would hardly be the first word to have been given an assist from the world of comics. Brainiac is thought to have its origins in an early issue of Superman, and the pejorative term sad sack had its roots in George Baker's comic strip of the same name.