The U.S. Supreme Court started its January session today by listening to arguments in a case that could have huge ramifications for unions in Hawaii.

Friedrichs V. California Teachers Association, challenges the ability of unions to collect mandatory dues.

Currently 25 states have “Right to Work” laws that prohibit compulsory union due. In the other states, including Hawaii, employees in unionized jobs (such as public school teachers) can opt out of paying dues that go toward political activities but not dues that support things like collective bargaining.

Teachers in the Friedrichs case are arguing that requiring public employees to pay union dues violates the First Amendment. According to the Center for Individual Rights, which is representing the anti-union teachers, mandatory dues violate “well-settled principles of freedom of speech and association.” The suit also argues that essentially all union activities, including collective bargaining, are inherently political.

EdSource has a pretty good and simple breakdown of the case on its website.

During oral arguments Monday, Supreme Court justices made statements that appeared to signal support for the anti-union teachers, according to Politico.

The Hawaii State Teachers Association is watching the case carefully, as is the University of Hawaii Professional Assembly.

“This case is designed to significantly weaken all public sector unions by claiming you don’t have to pay a thing to receive the benefits of the contract,” UHPA Executive Director Kristeen Hanselman says in a report on the UHPA website. “It is a veiled attempt to cripple UHPA and other public sector unions and threatens the rights and protections of our members that are only achieved through collective bargaining.”

HSTA had 1,2444 active members in 2014 and collected $6.8 million in membership dues in 2013, according to its annual 990 report to the Internal Revenue Service. UHPA collected $3.1 million in membership dues in 2013.

Though it will likely be months before the Supreme Court issues its decision, some unions are already trying to figure out how they would handle an adverse ruling.

Hanselman notes on the UHPA website that union leaders are “preparing alternative approaches” to maintaining UHPA’s capacity should laws change in Hawaii as a result of the case.

The ruling would only impact public sector unions, according to Politico.