It happens almost every day: a policeman catches sight of a suspicious character, stops him and frisks him. But doesn't the Fourth Amendment specifically bar "unreasonable searches and seizures?" It does indeed, said the Supreme Court last week, but the operative word is "unreasonable." Speaking for an 8-to-1 majority, Chief Justice Warren held that the Constitution permits a policeman to accost an individual if there is good reason to suspect that he is up to no good, and to search him for weapons if there is good reason to suspect that he may be armed.
The qualifications are not idle, said the...