The Supreme Court yesterday affirmed the federal government's power to order out state National Guard troops for training missions over the protest of governors who have political objections to the exercises.

In a unanimous opinion by Justice John Paul Stevens, the court said Minnesota Gov. Rudy Perpich (D) did not have authority to stop Minnesota National Guard troops from being sent on training missions in Central America. Massachusetts Gov. Michael S. Dukakis (D) also had opposed sending his state's troops on such exercises.

Perpich had asked the court to review the constitutionality of a 1986 law, known as the Montgomery Amendment, that prohibits governors from vetoing federal orders to place the troops on active duty because they disagree with the mission's location or purpose.

Perpich and other governors had complained that the law violated the Constitution's Militia Clauses, which give Congress power to organize the militia but reserves to the states the right to train it.

The court said in Perpich v. Department of Defense that the Montgomery Amendment -- named for its sponsor, Rep. G.V. "Sonny" Montgomery (D-Miss.) -- does not infringe on the state's constitutional rights but "merely recognizes the supremacy of federal power in the area of military affairs."

In another ruling yesterday, the court gave police new authority to stop and question suspects on the basis of anonymous telephone tips.

Splitting 6 to 3, the court said such tips may be reliable enough to give police officers the "reasonable suspicion" they need to justify "investigatory stops," in which suspects are detained and questioned but not formally arrested.

The ruling continued the court's trend of easing standards police must meet in dealing with suspects. Police need probable cause to make arrests, but the court has allowed them to stop and question suspects on "reasonable suspicion" of criminal activity.

Yesterday's decision, Alabama v. White, involved an anonymous telephone tip to Montgomery police that Vanessa White would be leaving an apartment building at a particular time in a brown Plymouth station wagon with a broken right taillight lens. The caller told police White would have about an ounce of cocaine inside a brown briefcase and would drive to a local motel.

Acting on that information, officers saw White leave the apartment, without a briefcase. She got into the station wagon and headed toward the motel. Police stopped White, she allowed them to search the car, and they found a locked brown briefcase containing marijuana. Later, they found three milligrams of cocaine in White's purse.

White sought to have the marijuana and cocaine thrown out as the fruit of an illegal detention, contending the police did not have reasonable suspicion necessary to justify the stop. An Alabama appeals court agreed.

In reversing that ruling yesterday and reinstating White's conviction for cocaine and marijuana possession, the court said White's was a "close case," but that "under the totality of circumstances the anonymous tip, as corroborated," had sufficient indications of reliablity to justify the stop.

Justice Byron R. White, writing for the majority, said the call "demonstrated inside information" about White's plans. "Because only a small number of people are generally privy to an individual's itinerary, it is reasonable for police to believe that a person with access to such information is likely to also have access to reliable information about that individual's illegal activities," he said.

Stevens, joined by Justices William J. Brennan Jr. and Thurgood Marshall, said the decision "makes a mockery" of the Fourth Amendment protection against unreasonable search and seizure, and leaves citizens at the mercy of "overzealous and unscrupulous" officers.

Also yesterday, the court declined to intervene in a dispute growing out of a settlement between the Teamsters Union and the federal government concerning accusations of union racketeering activity.