(CBS) — The Amalgamated Transit Union claims the CTA has banned workers from sharing literature and talking about anything related to the 2015 Mayoral Race. As a result, they’ve filed a lawsuit claiming a violation of First Amendment rights of transit workers.

“As is well known, the locals have endorsed a candidate, Commissioner Garcia, and they want to distribute to their materials to their own members in their break rooms while off duty and the CTA is telling them they can’t do that even though these break rooms have been open for a great deal of speech of all types in the past,” said attorney Sean Morales Doyle.

Tuesday, ATU filed a lawsuit in U.S. District Court for the Northern District of Illinois alleging that CTA is violating the First Amendment Rights of transit workers.

“Rahm has essentially installed a free speech red light camera for every public workplace in the city and we are not going to stand for it,” said Carlos Azevedo, ATU Local 241.

The union claims CTA posted memos in bus garages and rail terminals barring employees from this kind of communication and warned of fines.

“It is our right to have freedom of speech on who we want to support in our training rooms where we are not working and we’re not going to stand for it. We’ve seen this before 30 years ago when Harold Washington was running and we’re not going to stand for it and that’s why we’re here today,” said Ken Franklin, President, ATU Local 308.

The union that represents 10,000 employees has endorsed challenger Chuy Garcia in the race for mayor.

The CTA says there are two state laws that strictly prohibit political activity on government property and on government time. The Mayoral runoff is next Tuesday, April 7.