IT’S NOT HARD to think of people we might like to see exiled from the District of Columbia on the grounds that they are dangerous, obnoxious or universally regarded as nuisances. Drunk drivers, to start with; dog owners who don’t clean up after their pets; pickpockets; possibly even politicians. But in the United States, where the Constitution confers certain rights and privileges of citizenship — including the right to domestic travel, according to the Supreme Court — it is all but unheard of for courts to banish individuals from entire states and localities.

That’s why the order by a D.C. Superior Court magistrate judge, who banned an antiabortion protester from returning to the District pending a court date next month, is so bizarre. What’s next — a federal judge ruling the entire Atlantic seaboard off-limits?

No doubt, the magistrate judge, Karen Howze, was within her rights to be annoyed at Rives M. Grogan, an antiabortion activist who for years has made a hobby of disturbing the peace and getting arrested for it, especially around Capitol Hill. On Inauguration Day, Mr. Grogan, bearing a ticket, passed through security, then climbed a tree on the Mall within view of the Capitol. He proceeded to spend five hours in his perch, during and after President Obama’s swearing-in and speech, waving a sign and shouting at the top of his lungs.

Authorities decided to let him be, until Mr. Grogan finally climbed down later in the day, whereupon he was arrested by U.S. Capitol Police. In the charging document, they accused him of disturbing the peace and, by breaking several branches above the heads of the crowd, “jeopardizing his life and the life of others.”

Hauled into Superior Court for at least the dozenth time in the past couple of years, Mr. Grogan faced federal prosecutors, who asked that the judge ban him from the Capitol grounds, House and Senate office buildings, the Library of Congress and the Supreme Court. Fair enough.

But Judge Howze went a giant step further. As a condition of his release pending trial, she ordered Mr. Grogan, who lives in Los Angeles, banished from the District in its entirety.

The judge’s order is a spectacular case of judicial overreach. Mr. Grogan protested it on First Amendment grounds, and justly so. It is remarkable that he would be banned from grinding his particular ax in the 68 square miles of the nation’s capital, where citizens have a right to petition for a redress of grievances. But really, this isn’t a only a First Amendment case.

Equally fundamental to his privileges as a citizen is the right to move about the United States freely, so long as in doing so he doesn’t imperil others. As Justice John Paul Stevens wrote in Saenz v. Roe (1999), the right to travel is “firmly embedded in our jurisprudence.”

If Mr. Grogan’s actions at the inauguration posed a threat to public safety, as the judge reasonably concluded, she could have prohibited him from climbing trees over the heads of others. But exiling loudmouths, exhibitionists and ideologues from the District is neither constitutional nor practicable. After all, Congress is located in the city, and it’s here to stay.