But the court heard a similar case a year ago, and it came down 4-4 after Justice Antonin Scalia died. Labor unions active in the public sector are already scrambling to deal with the expected result of the case.
The Supreme Court granted the case - brought by Mark Janus against the American Federation of State, County, and Municipal Employees, Council 31, in IL - in late September, once Gorsuch had joined the court, and heard arguments on Monday.
Unionized workers filled a city block as they marched in downtown Pittsburgh Monday - the same day the U.S. Supreme Court heard arguments in a major case involving public sector unions.
Back in 2015, the court almost voted to overturn the rule, but the untimely death of Justice Antonin Scalia led to a four-to-four deadlock allowing the rules to stand.
Because President Donald Trump appointed Gorsuch, union members are anxious that the court will rule against them.
"The Janus case is an attack on working families that will allow employers to lower wages and take bigger profits", South Bay Labor Council Executive Officer Ben Field declared ahead of the #WeRise rally.
Gorsuch, President Donald Trump's appointee to fill Scalia's seat, has been seen as providing the fifth vote for the conservatives, but he was uncharacteristically quiet during Monday's argument. Janus and the conservative interests that back him contend that everything unions representing public employees do is political, including contract negotiations. They say that if non-members don't have any obligation to pay fair share fees for the collective bargaining obligations, they would become free riders, benefiting from the representation without sharing the costs.
"If people don't have to pay anything, we're going to end up underfunding our unions, and eventually they'll be crippled by it".
"In every public sector jurisdiction in every state, you could not require a non-member of the union who doesn't want to pay fees to pay fees", she said.More news: Second Russian athlete fails doping test
It's part of the Janus v. AFSCME lawsuit.
"Let's face it, not everybody wants to be in the union", he said.
If justices side with IL employee Mark Janus, non-union members won't have to pay those fees, but they would still receive representation.
In a similar 2016 case, justices ended in a 4-to-4 deadlock over the fate of fair share fees.
"Probably their goal is to eventually get rid of the unions", Green told WFMZ.
Union officials said a ruling in favor of Janus would effectively starve the union of funds.
Hundreds of union supporters including faith leaders, elected officials and immigrant rights groups attended the rally at the State Capitol. "I am confident that they will side with free speech for the people of our great nation", Rauner said of the justices, following the arguments.
"We will not allow any court case, any legislation, or any propaganda campaign take away our unions".
"What we're talking about here is compelled justification and compelled subsidization of a private party, a private party that expresses political views constantly", Kennedy said.