THe Supreme Court yesterday rejected a government plea to decide whether American judges can examine the motives behind an official act taken by a foreign power within its own borders.

The justices made no comment on why they turned down a Justice Department petition to review a decision in a $375 million antitrust suit brought by independent oil producer Nelson Bunker Hunt against the seven lasrgest integrated oil companies.

The suit arose from the 1973 nationalization by the revolutionary government of Libya of Hunt's oil-producing concession.

He and the "Seven Sisters" - Mobil. Texaco, Standard Oil of California, British Petroleum, Shell, Exxon and Gulf - had been parties to "safety net" agreements under which the major oil companies were to make up crude oil lost by a Libyan producer because of expropriation.

In one of four claims in the anti-trust suit. Hunt charged that the seven companies violated the agreement by trying to disadvantage Libyan crude against their own Persian Gulf crude and by trying to eliminate him from the industry.

The Second Circuit U.S. Court of Appeals dismissed Hunts claim by invoking the so-called "Act of State doctrine" that bars the courts of one country from judging the internal officials acts of another.

The court said that it couldn't look at Libya's motive in the nationalization, as Hunt wanted, without sitting in judgement on its validity, which the doctrine forbids it to do.

In a brief requested by the Supreme Court, Solicitor General Wade H. McCree contended that the doctrine permits judicial examination of Libya's motive. Previous court rulings do not preclude "all lines of investigation that may embarrass a foreign state or affect the political branches' conduct of foreign relations," he said.