The National Rifle Association, having beaten back attempts by Congress to restrict semiautomatic assault rifles, has set its sights on a new target: it has asked the Supreme Court to overturn the ban on private ownership of fully automatic machine guns.

The move has outraged law enforcement groups and gun control advocates who charge that it shows "blatant disregard for public safety and law enforcement officers" on the street.

But some legal scholars say a Supreme Court ruling on the request could clear up one of the more contentious issues of constitutional law: Precisely what does the Second Amendment to the U.S. Constitution mean when it states, "A well-regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."

"The Supreme Court shouldn't even dignify the petition by hearing this case," said Prince George's County Police Chief David B. Mitchell at a recent news conference on behalf of the Police Executive Research Forum. As patrol officers routinely stopping traffic violators, he said, "We're taking {semiautomatic} Uzis off the street; we're taking MAC-11s off the street right now . . . We are not equipped to face people armed with machine guns. They have no place in civilized society."

But NRA lawyers argue that broad constitutional issues are at stake. In their brief defending a Georgia gunmaker's application to manufacture and possess a machine gun, attorneys for the NRA's Firearms Civil Rights Legal Defense Fund called the four-year-old prohibition "the first ban on firearms possession by law-abiding citizens in American history.

"At this time of the bicentennial of the Bill of Rights, this court should not allow. . . a fundamental infringement on the right of the people to keep arms guaranteed by the Second Amendment," the petition said.

At first glance, the machine gun issue may seem absurd. Not even the NRA argues such guns have a legitimate hunting purpose.

The NRA's position has been opposed by the Justice Department, which recently filed its brief with the Supreme Court accepting a lower court ruling that the Second Amendment "does not absolutely bar all congressional regulation of firearms."

But the Supreme Court has not addressed the issue of the meaning of the Second Amendment in more than 50 years. With the rising tide of gun-using violence nationwide, considerable debate has arisen over whether the amendment's language protects individual owners of all firearms or if it was intended mainly to protect the weapons of state militias.

"They do have a duty to confront this issue," said Sanford Levinson, a professor of law at the University of Texas and author of a recent article in the Yale Law Journal entitled "The Embarrassing Second Amendment." "There are at least 3 million {NRA members} who take the Second Amendment seriously and who feel ignored by the justices."

The prospect of a high court ruling also raises the stakes in the machine gun case, said Barbara Lautman, executive director of the Center to Prevent Handgun Violence. If the Supreme Court takes the case and adopts the NRA's position, "every gun control law in the country would be in jeopardy," she said.

Under a 1934 law, passed in response to the violence of the Prohibition era, all privately owned machine guns had to be registered with the Bureau of Alcohol, Tobacco and Firearms, a process that required purchasers to be fingerprinted for a background check and to obtain clearance from local police.

Yet only about 125,000 machine guns were legally registered by 1986 -- a fraction of the 200 million handguns, rifles and other firearms estimated in the United States.

"Why they want to own them I don't know," said James Jay Baker, the NRA's director of federal affairs. "But the fact is, there are 125,000 people who for whatever reason are willing to go through all the hoopla" to register machine guns and should be given the right to do so, he said.

The rules changed in 1986 when Congress passed the Firearms Owners Protection Act. Sponsored by Sen. James A. McClure (R-Idaho) and Rep. Harold L. Volkmer (D-Mo.) with NRA backing, the law eliminated some record-keeping requirements for gun dealers and allowed citizens to buy "long guns," or rifles, across state lines.

But one amendment, sponsored by Rep. William J. Hughes (D-N.J.) at the request of law enforcement groups, banned ownership or transfer of new machine guns after May 19, 1986, except those "under the authority of the United States" or any state agency.

The Treasury Department has interpreted the "under the authority" clause to apply only to U.S. military and law enforcement organizations, a claim the NRA charges is far too narrow and a "misinterpretation" of congressional intent.

The issue came to a head after J.D. Farmer, a Georgia gun manufacturer, applied to BATF in 1987 for a license to manufacture a new machine gun for his private possession. When BATF turned him down, Farmer filed suit in federal court.

U.S. District Judge Owen Forrester ruled in Farmer's favor, but the Court of Appeals reversed the decision, concluding that nothing in the Second Amendment barred Congress from banning private ownership of weapons of war.