The Supreme Court yesterday broadened the power of the states to tax business connected with interstate commerce by unanimously overturning a ruling that had been in force for a quarter-century.

The court held that Mississippi could levy sales taxes on Complete Auto Transit, Inc., a Michigan firm retained by General Motors Corp. to pick up GM vehicles in Jackson, Miss., and deliver them to dealers throughout the state. The vehicles were made outside Mississippi and delivered to Jackson by rail.

The Mississippi State Tax Commission told Complete Auto that it was assessing it $165,151 in taxes and interest for a four-year period ending in 1972 under a state law directing collection of taxes for "the privilege of . . . doing business" in the state.

The company paid the sum under protest and then sued. It claimed that its transportation was but one part of an interstate movement that was insulated from state taxation by the Constitutional provision giving Congress exclusive power to regulate interstate commerce.

Complete Auto relied mainly on a 1951 Supreme Court decision that barred a state from taxing the "privilege" of engaging in an activity that is part of interstate commerce.

The Mississippi Supreme Court ruled that the state tax was valid and was not prohibited by the 1951 decision, which established the so-called Spector rule in a case involving a Missouri corporation engaged entirely in interstate trucking.

In an opinion affirming the Mississippi decision, justice Harry A.Blackmun said for the high court that "the Spector rule, as it has come to be known, has no relationship to economic realities. Rather it stands only as a trap for the unwary draftsman" who uses the word "privilege" in a state law imposing what actually is a sales or gross recepits tax, he said.

"If Mississippi had called its tax one on 'net income' or on the 'going concern value' of appellant's (Complete Auto's) business, the Spector rule could not invalidate it," Blackmun wrote.

The court took other actions:

Expired Union Contracts

A contract between Nolde Brothers, Inc., and Local 358 of the Bakery and Confectionery Workers Union, AFLCIO, provided for binding arbitration of "any grievance" arising between the company and its bakery employees in Norfolk, Va.

The union terminated the agreement in 1973 after it had expired and after negotiations had failed to produce a new one. Finally, the company, threatened by a strike, told the union on Aug. 31, 1973, that it was going to close the plant permanently that day.

Nolde Brothers refused to pay severance pay and refused to arbitrate when the union filed a grievance on the ground that the union's voluntary termination of the agreement left no severance-pay issue to arbitrate.

The Fourth Circuit U.S. Court of Appeals, reversing a lower court, held that claims arising by reason of the agreement survived its termination and required arbitration.

In the past, the Supreme Court had held to the principle that a party to a labor contract cannot be compelled to arbitrate any matter in the absence of a contractual obligation to do so.

But in an opinion for the court, Chief Justice Warren E.Burger said adherence to that principle "does not require us to hold that termination of a collective-bargaining agreement automatically extinguishes a party's duty to arbitrate grievances under the contract." Justice Potter Stewart, joined by Justice William H.Rehnquist, dissented.

Union Members vs. Union

The laste Richard T.Hill was elected in 1965 as vice president of Local 25 of the United Brotherhood of carpenters and Joiners of America. AFLCIO, which operates an exclusive hiring hall that refers carpenters for jobs in the Los Angeles area.

Soon thereafter, he got into sharp disagreements over union policies with some of its officials. As a result, he charged in outrageous conduct, threats and intimidation that resulted in emotional distress and bodily injury and saw to it that he could'nt get jobs.

A California state court awarded Hill $7,500 actual and $175,000 punitive damages. But the California Court of Appeal reversed on the ground that the conduct at the crux of the disputes was in the jurisdiction of the National Labor Relations Board.

The Supreme Court nullified that ruling and sent the case back for new proceedings. In an opinion for a unanimous court Justice Lewis F.Powell Jr. said that federal law does not prempt action for intentional infliction of emotional distress, does not protect "outrageous conduct" and does not remove the substantial interest of a state in protecting its citizen from the kind of abuse of which Hill had complained.