Justice Neil Gorsuch likely holds the key vote in a major labor case that drew dueling protests outside the Supreme Court building for Monday’s oral arguments, but he did nothing to tip his hand about his thinking.

Gorsuch did not ask a question during an hour of arguments, while the other eight justices appeared to be equally split along ideological lines. The case asks the justices to overturn a decades-old precedent and deal a financial blow to the unions that represent teachers and other public-sector employees.

The other eight justices had already heard oral arguments in a nearly identical challenge in 2016. But the death of Justice Antonin Scalia that year meant the remaining justices deadlocked 4-4 and couldn’t rule on the issue.

Now Gorsuch is on the bench. And this time, Illinois state employee Mark Janus is arguing that the fees public-sector unions collect from nonmembers to cover the cost of actions that help all employees are coerced speech that violates his First Amendment rights.

The justices are expected to rule on the case before the end of the term in June. A large crowd of organized protesters from both sides rallied on the sidewalk in front of the court, bearing signs including “America needs union jobs” and “No one should be forced to fund causes they don’t believe in.”

Gorsuch is considered a reliably conservative justice, but his silence Monday will keep experts guessing about whether he will side with the conservative wing of the court and overturn a ruling from the 1970s that allows unions to collect those fees.

Chief Justice John G. Roberts Jr., along with Justices Anthony M. Kennedy and Samuel A. Alito Jr., focused on the idea that requiring the fees forces employees who disagree with the union to subsidize its activities.

“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.

Justice Sonia Sotomayor, part of the court’s liberal wing, pointed out that the Supreme Court has drawn a big distinction between compelled speech and compelled subsidy for something like state bar associations for lawyers, where someone isn’t stopped from speaking out publicly on an issue.

“Bar members can come out any day they want and say they don’t take the same position on a policy question as the bar association,” Sotomayor said. “Any union member is free to get up publicly in any setting he or she wants to say they don’t agree with the position the union is taking.”

Another liberal justice, Elena Kagan, focused on the negative effects of a ruling against unions. She said contracts would have to be redone in 23 states, the District of Columbia and Puerto Rico because laws on the issue in those jurisdictions would then become unconstitutional.

David Frederick, a lawyer arguing for the American Federation of State, County and Municipal Employees, the labor union in the case, told the justices that state legislatures, city councils and school districts will have to start over when it comes to negotiating with state employee unions if the court overturns Abood v. Detroit Board of Education.

That 1977 decision has allowed unions to avoid “free rider” public employees who get the benefits of a union’s work without paying any dues.

“The fees are the tradeoff. Union security is the tradeoff for no strikes,” Frederick said. “And so if you were to overrule Abood, you can raise an untold specter of labor unrest throughout the country.”

AFSCME, which is made up of 3,400 local unions representing more than 1.4 million members, overwhelmingly supports Democratic candidates and causes.

The case is Janus v. AFSCME, Docket No. 16-1466.