As hundreds of union leaders and members gathered outside the courthouse with protest signs, the U.S. Supreme Court heard oral arguments on Jan. 11 in Friedrichs v. California Teachers Union, a case that threatens to undermine the ability of the UFT and other public-sector unions to advocate effectively on behalf of their members.

The Friedrichs case, which seeks to overturn a ruling made by the Supreme Court 40 years ago, is funded by the anti-union Koch brothers and other right-wing organizations that seek to gut union power.

Under current law, public employees covered by union contracts may opt out of paying for the political activities of their unions. But states may pass laws that allow unions and public employers to agree that those dissenting members are required to pay a fee to cover their portion of collective-bargaining costs. At the heart of the case is whether the collection of those fees violates these non-members’ First Amendment free-speech rights.

A transcript of the arguments posted on the website of the high court showed four liberal justices — Sonia Sotomayor, Elena Kagan, Ruth Bader Ginsburg and Stephen Breyer — aggressively questioning Michael A. Carvin, the lawyer representing Rebecca Friedrichs and nine other California teachers, about equating collective bargaining with political speech.

“We’re talking about six people in a room bargaining about wages, hours and working conditions,” said Justice Breyer. “That’s pretty far removed from the heart of the First Amendment.”

Edward C. Dumont, speaking on behalf of the attorney general of California, argued that agency-fee arrangements benefit government employers because they help ensure stable labor-management relations. “In the collective-bargaining context, what the employer needs is to get one agreement with one group of employees, which we do by having one union,” he said.

Dumont was pointedly questioned by the more conservative justices, including Chief Justice John Roberts, Antonin Scalia, Samuel Alito and Anthony Kennedy. Clarence Thomas was silent; he has a long record of not speaking up during the oral arguments but voting with the conservative faction.

Scalia summed up the position of his fellow conservative judges when he told Dumont: “The problem is that everything that is collectively bargained with the government is within the political sphere, almost by definition. Should the government pay higher wages or lesser wages? Should it promote teachers on the basis of seniority? … [A]ll of those questions are necessarily political questions.”

David C. Frederick, representing the California Teachers Association, argued that overruling the precedent for collecting agency fees would disrupt labor-management systems “in nearly half the country.” (Twenty-three states, including New York and California, have passed laws establishing agency-fee arrangements.) Frederick noted the wide range of benefits covered by the fees, including teacher training.

The union lawyer challenged Justice Kennedy’s claim that existing law silences “a whole class of persons.” “Their speech isn’t silenced,” Frederick said. “They are paying a service fee so that the exclusive representative can negotiate their health and welfare benefits, their mileage reimbursement … voluntary teacher transfer policy… duty-free breaks ….”

The court is not expected to issue a decision until the end of its session in June.