The Supreme Court seemed likely Wednesday to reinstate the trespassing conviction of a man who was caught protesting military activities in a place he had been ordered to avoid: the zone designated for demonstrators outside the main gate at a California air force base.

Protester John Dennis Apel tried to persuade the court that his case raised important First Amendment issues. But the justices focused instead on the federal law under which Apel was convicted, which gives commanding officers authority to prevent people from entering military installations.

When Erwin Chemerinsky, the constitutional scholar representing Apel, tried to get the court to turn to Apel’s free speech rights, Justice Antonin Scalia cut him off.

“You can raise it, but we don’t have to listen to it,” Scalia said.

Apel has been visiting the designated protest zone at Vandenberg Air Force Base on the central California coast for 14 years. He had previously run into trouble at the base when, in 2003, he threw 4 ounces of his own blood on the Vandenberg sign.

That incident led to the first of several orders barring him from entering any part of the base, including the protest area on a public highway that passes near the main gate. The military owns the highway but grants the state and Santa Barbara County an easement so the public can use it. The protest zone was set up in the late 1980s as part of the settlement of a federal lawsuit.

A federal appeals court overturned Apel’s conviction because the military shares control of the highway with local authorities. Chemerinsky also said the law cannot be enforced outside the base fence and green line painted on the road that marks the start of the area in which access is restricted.

There was little support on the court to reading the law in favor of Apel.

Anthony Kennedy was one of several justices who said that allowing the public to use the highway under an agreement with local authorities does not mean that the military has forfeited all control. “The military commander can make reasonable regulations,” Kennedy said, suggesting that he sees the order barring Apel as reasonable.

The Obama administration is eager to get the ruling from the 9th U.S. Circuit Court of Appeals erased from the books because it could affect similar arrangements at roughly three dozen bases in the nine Western states covered by the San Francisco-based court.

The justices could throw out that ruling and yet still give the appeals court the chance to consider Apel’s First Amendment claims. The administration favors this approach, although it said Apel’s rights were not violated.

A decision is expected by late June.