High-visibility protests here against the South African government have raised objections on Capitol Hill to a District law that long has been a sore point with demonstrators, one that keeps them nearly two football fields away from the foreign embassy they are picketing.

Sen. Arlen Specter (R-Pa.), chairman of the Senate District appropriations subcommittee, warned that Congress could step in and change the restrictions, which he regards as an undue limit on free speech, if the city does not.

"My legal judgment is that the statute is overly broad and not reasonably related to security," Specter said after a hearing yesterday on the issue.

State Department, Justice Department and law enforcement officials, however, testified that the requirement is necessary to provide adequate security for the 136 foreign embassies located here.

And Robert Lamb, State Department assistant secretary for administration, argued that this would be the wrong time to relax security rules here, since the United States is currently trying to get other countries to beef up efforts to protect American diplomats from terrorists.

"The line between the peaceful demonstrators and the terrorists is a thin one," Lamb said.

The District law, approved by Congress in the 1930s before the city passed its own legislation, prohibits displays critical of a foreign government within 500 feet of a foreign embassy.

Specter also objected yesterday to the District police department's role in making "arrests by appointment" at the South African Embassy, where demonstrators appear at regular times and decide who among themselves will violate the law in order to get arrested and bring more attention to their cause.

"They should be out arresting drug dealers," the senator said. He called Police Chief Maurice Turner to task, saying "I'm not sure you're promoting public safety by participating in staged arrests."

The demonstrations continued at the embassy yesterday afternoon and eight more persons were arrested.

D.C. Del. Walter E. Fauntroy, one of those originally involved in planning the demonstrations and the first person arrested, testified that the 500-foot limit "hinders the exercise of free expression and free speech" and should be reduced.

Art Spitzer, legal director of the Washington-area American Civil Liberties Union, said he recently noticed a demonstration outside the Brazilian Embassy, but it was a protest against British activities in Northern Ireland and was aimed at the British Embassy up the street. Keeping protesters so far away, and thus muddling their expressions of opinion, is unnecessary, he said.

D.C. City Administrator Thomas Downs said yesterday the city does not plan to change the law restricting protests.

But Specter said there are "severe constitutional problems" with the law and said it could be rewritten to allow peaceful protests to get closer to embassies. U.S. law provides that protests at foreign missions in other parts of the country must be 100 feet away, but the District may have unique circumstances that would necessitate different restrictions, he said.

The District should be given a chance to respond to the need for change but Congress would be justified in stepping in if the city does not, the senator added.

Specter also said the District should be able to arraign people 24 hours a day rather than requiring those arrested after lunch to stay overnight, creating expense for the city and inconvenience for persons who should be out on bail.