Natural gas committed to the interstate market can't be removed from it without the approval of a federal regulatory agency, the Supreme Court ruled 8 to 0 yesterday.

The ruling reversed the 10th U.S. Circuit Court of Appeals in a case involving the Unted Gas Pipe Line Co., an interstate carrier; the McCombs Group, a Texas producer, and what is now the Federal Energy Regulatory Commission.

In a separate natural-gas case, the court agreed to decide whether Louisiana may impose a tax on the fuel that passes through its boundaries on its way to consumers elsewhere.

Eight states, including Maryland, estimate that the tax would add about $225 million a year to consumer bills, including $3.3 million in the Washington area. The other states are Illinois, Indiana, Massachussets, Michigan New York, Rhode Island and Wisconsin.

The states' attorneys general contend that the tax, which Louisiana initiated April 1, unconstitutionally interferes with interstate commerce. The Justice Department, representatives of the industry, and Alabama's attorney general supported their plea.

Employing a rarely used power, the Supreme Court accepted the case for argument and decision - in the term starting in October - even though it hasn't been heard in a lower tribunal.

In the pipeline case, the owner of a tract in Karnes County, Tex., contracted to sell all the gas produced from it to Unted Gas. On that basis, the owner obtained from the Federal Power Commission, predecessor to FERC, a certificate of convenience and necessity authorizing the sale.

That was in 1953. In 1966, however, a successor owner of the tract notified United that the existing wells were depleted - but did not seek the permission to abandon production required by the Natural Gas Act of 1938.

Later, however, the McCombs group, which meanwhile had acquired rights to part of the tract, drilled more deeply in it than anyone had done before and discovered new gas reserves. In 1972, McCombs contracted to sell this gas - for industrial use within Texas - to E.I. duPont de Nemours & Co

When United Gas Pipe Line learned of the production, it asserted its rights under its contract, which gave it rights to all gas produced from the property until 1981.

The FPC ruled for United, holding that the gas sales to Du Pont violated the 1938 law. The 10th Circuit set aside the order but was overruled yesterday.

In the opinion for the unanimous Supreme Court, Justice Thurgood Marshall wrote, "Congress could not have been more explicit in establishing commission approval as a prerequisite for lawful abandonment of service within its jurisdiction."

Justice Potter Stewart did not participate.

The court took other actions. "Situtions Wanted

In a case involving the Pittsburgh Press, the court left intact a ruling that a Pennysylvania human-rights law violates the First Amendment by forbidding "situations wanted" classified advertisements in which a job-seeker suggests, in any manner, "race, color, religious creed, ancestry, age, sex or national origin." Labor Relations

The court preserved a victory for the National Labor Relations Board by refusing to review a 7th U.S. Circuit Court of Appeals decision that an employer can't use a charge of sex discrimination in a union to oppose certification of the union as a collective-bargaining agent.

In other actions, the Associated Press reported: Offshoire Oil

The court agreed to decide whether Alaska or the federal government owns an offshore area thought to be rich in oil and natural gas.

The justices, in effect, gave the Carter administration permission to sue Alaska in the nation's highest court to settle the ownership dispute. Loan Default

The court agreed to review a decision requiring lenders to tell borrowers that if they default on their loan and full payment is demanded, unearned finance charges will be rebated.

The justices voted to hear an appeal by the Ford Motor Credit Co., a subsidiary of the Ford Motor Co., that the Truth in Lending Act does not require such disclosure.

The court's eventual decision could affect an estimated 60 million U.S. consumer credit contracts representing more tha $265 billion in total consumer installment debts. Tanker Subsidy

The court agreed to study a decision blocking a supertanker built with the help of $27.2 million in federal subsidies from hauling Alaskan oil to domestic ports.

The justices said they will review an appeals court ruling that allows the T. T. Stuyvesant to be used only in foreign trade. Even before the ship was completed two years ago, its market in foreign trade had disappeared.

At issue is the secretary of commerce's authority to waive trade restrictions placed, by law, on vessels that receive federal construction subsidies.