Should the police be allowed to affix an electronic tracking device to a suspect's car without a warrant and follow his every movement for a month? That was the question at an oral argument at the Supreme Court on Tuesday. The justices expressed unease with such pervasive surveillance, with one comparing it to George Orwell's "1984."

Their misgivings reflect a sense on the part of many Americans, including this editorial board, that there's something creepy about round-the-clock electronic surveillance. But when they decide the case of Antoine Jones, a suspected drug dealer who was arrested after being monitored by a global positioning system, they will have to base any decision in Jones' favor not on creepiness but on the Constitution. Fortunately, that document, interpreted in light of technological advances, supports a ruling that GPS surveillance without a warrant violates the 4th Amendment.

In his argument, Deputy Solicitor Gen. Michael Dreeben asked the court to treat GPS tracking the same way it treats visual observation of a suspect on a public street. "What a person seeks to preserve as private in the enclave of his own home or in a private letter or inside of his vehicle when he is traveling is a subject of 4th Amendment protection," Dreeben said. "But what he reveals to the world, such as his movements in a car on a public roadway, is not."