The Entertainment Software Association is suing the Chicago Transit Authority for unfairly targeting video games and banning advertisements of Mature- or AO-rated titles. ESA CEO Mike Gallagher states that video games are under the same First Amendment protections as other entertainment mediums. The double-edged sword here is that either the CTA can ban R-rated and TV-MA advertisements to make the rule fair across the board, or the ESA will likely win given past history.
The anti-video game ad ordinance (CTA Ordinance 008-147) was enacted in January of this year, which prohibits advertisement and marketing that "identifies a video or computer game rated "Mature 17+" (M) or "Adults Only 18+" (AO)." We're following up with the ESA for more details and will update if we receive any more information.
Update: We've uploaded the full complaint here. (Warning: PDF link)