Dennis Apel attends a vigil on Nov. 6 at Vandenberg Air Force Base in California. (Jamie Rector/Post)

The Supreme Court on Wednesday unanimously overturned an appeals court ruling that had favored an antiwar protester who was arrested for demonstrating at a sprawling U.S. Air Force base in California, but the justices did not get into the issue of free-speech rights.

The court threw out a ruling by the U.S. Court of Appeals for the 9th Circuit in San Francisco, which had overturned lower court convictions of John Dennis Apel, a longtime peace activist who was arrested several times in 2010 for violating a federal law that forbids a person from entering a military base after being ordered not to do so by the commanding officer.

Apel, 63, has protested at Vandenberg Air Force Base for more than a decade. But he was barred from the base after throwing blood on the Vandenberg entrance sign in early 2003 in a protest as the United States was preparing to invade Iraq.

He and like-minded activists have continued to protest on the first Wednesday of every month at a site along the Pacific Coast Highway that has been set aside for protesters since 1989. The highway, a segment of California State Route 1, runs through the 22-square-mile base north of Santa Barbara.

Because of his earlier protest activities, the Vandenberg commander has barred Apel from entering any part of the installation, including the designated protest area.

In overturning Apel’s convictions, the Court of Appeals for the 9th Circuit said commanders have authority to bar people only on property exclusively controlled by the U.S. government. It noted that the base shares control of the highway with the state of California and the county of Santa Barbara.

In an opinion written by Chief Justice John G. Roberts Jr., the high court held that a base’s designated protest area and an easement for a public road are part of the military installation. Therefore, the base has control over who enters and uses such facilities, the opinion said.

Although the ruling was unanimous, Justice Ginsburg Ruth Bader Ginsburg filed a concurring opinion joined by Justice Sonia Sotomayor, and Justice Samuel A. Alito Jr. also filed a concurring opinion.

In oral arguments in December, Apel attorney Erwin Chemerinsky repeatedly tried to raise Apel’s constitutional rights, but the justices shut him down.

“You keep sliding into the First Amendment issue, which is not the issue” on which the court accepted the case, Justice Antonin Scalia said. “We’re only interested in whether the statute applies.”

Chemerinsky said the statute must be considered in tandem with Apel’s free-speech rights.

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

Assistant Solicitor General Benjamin J. Horwich, representing the government during the oral arguments, said the appeals court decision imposed an “exclusive possession” requirement that “isn’t anywhere in the text of the statute.”

Foreshadowing Wednesday’s ruling, most justices seemed to agree with Horwich in December, saying that the base commander does not cede control over who may be on the base just because civilians are allowed to travel on major highways through it. Apel is allowed to drive on those roads also, as long as he does not stop and get out.