Police arrest demonstrators after they tore down a barricade and took to the steps of the U.S. Supreme Court building, on the anniversary of the Citizens United decision, in Washington, Jan. 20, 2012. (Jonathan Ernst /Reuters)

Supreme Court justices found themselves a bit spatially challenged last month, when they heard oral arguments about a Massachusetts law that keeps people 35 feet from the entrance of an abortion clinic.

From here to the back of the courtroom, Justice Elena Kagan asserted. No, more like two car lengths, offered Justice Sonia Sotomayor. Far enough that one would have to shout to be heard by someone entering, Justice Antonin Scalia said.

But there is no mystery about how far a demonstrator may advance when trying to make a point at the Supreme Court.

It is beyond the justices’ grand courtroom, past the Great Hall, down the court’s iconic front steps, across the 252-feet by 98-feet oval marble plaza, and down eight more steps to the sidewalk along First Street.

In other words, the whole city block on which the Supreme Court sits is off-limits to protesters, save for the sidewalks that ring it. It has been that way, more or less, since 1949, when Congress decreed:

“It is unlawful to parade, stand, or move in processions or assemblages in the Supreme Court Building or grounds, or to display in the Building and grounds a flag, banner, or device designed or adapted to bring into public notice a party, organization, or movement.”

But the restrictions on protests at the Supreme Court are under legal attack all over the city, following a decision last June by a federal judge that the 1949 statute went too far.

“It cannot possibly be consistent with the First Amendment for the government to so broadly prohibit expression in virtually any form in front of a courthouse, even the Supreme Court,” U.S. District Judge Beryl Howell wrote in a 68-page opinion.

Washington attorney Jeffrey Light has challenged the restrictions on behalf of Occupy DC protesters who were arrested at the Supreme Court and has brought a lawsuit against the regulation prohibiting protests that Chief Justice John G. Roberts Jr. approved after Howell’s decision.

But Light, who is affiliated with The Rutherford Institue, said that those are on hold while the government appeals Howell’s ruling to the U.S. Court of Appeals for the D.C. Circuit. Howell threw out the conviction of Harold Hodge of southern Maryland, who was arrested in January 2011 for standing on the plaza wearing a 3-by-2 foot sign that said, “The U.S. Gov. Allows Police to Illegally Murder and Brutalize African Americans And Hispanic People.”

The government’s appeal, filed on behalf of Supreme Court Marshal Pamela Talkin and D.C. U.S. Attorney Ronald C. Machen Jr., argues that it is logical to prohibit demonstrations at the Supreme Court in a way that might violate the First Amendment when applied to other government buildings.

“It is well established that the government has a legitimate interest in limiting picketing or demonstrating near courthouses,” Assistant Attorney General Stuart F. Delery writes.

“Unlike other parts of government, courts do not make decisions by reference to public opinion.”

The Supreme Court noted such arguments in 1983, in deciding a case brought by a protester named Mary Grace. Grace was arrested in 1980 on the sidewalk in front of the court for carrying a sign that reprinted the words of the First Amendment.

The justices ruled for Grace, saying that protesters could not be banned from a traditional public forum such as a sidewalk, even if it was in front of the Supreme Court. But they did not address the subject of protesters on the court’s grounds.

In its appeal of Howell’s ruling, the government points out what anyone who happened by the Supreme Court on the day of a big case knows: Demonstrations on the sidewalks occur all the time.

“Such protests are readily seen by the public and regularly covered by the press, and provide an adequate avenue for speech,” the brief states.

But Light said that that’s not enough.

“I don’t think the government gets to decide what places are right or wrong for protest,” he said in an interview.

The steps of the court provide an iconic backdrop for speech, he said. And barring activists from the plaza means they can’t approach visitors to the court or hand leaflets to those standing in line to enter the building.

Light and his client are supported by the American Civil Liberties Union of the Nation’s Capital, which says that a courthouse is traditionally seen as a forum for the public.

“Citizens view the ‘courthouse steps’ as an extension of the town square — a place to air their grievances with the judicial system, or the government or society more generally,” said the brief filed by Arthur B. Spitzer. “The United States Supreme Court is no different from other courts in this regard.”

Spitzer’s unusual brief is filled with photographs that show protests at courthouses across the country, and “expressive activity” at the Supreme Court itself. One shows the late Justice Thurgood Marshall — then a litigator — explaing a civil rights case to members of the “Little Rock Nine.” Another is of challengers Jeff Zarrillo and Paul Katami kissing after the court’s action last June that let same-sex marriages resume in California.

Nor is the plaza ban consistent, the ACLU argues. After every major argument, lawyers and parties to the case may gather on the plaza to address the media. And the brief said the court allows the group Faith in Action to hold group prayer sessions on the plaza to commemorate the National Day of Prayer.

Spitzer says it matters for a number of reasons whether demonstrations are allowed on the plaza rather than eight steps below on the sidewalk, but “it’s more the principle of the thing.”

For previous High Court columns, go to washingtonpost.com/fedpage.