Sen. Charles M. Mathias (R-Md.), said last night that the United States must move its foreign policy into "the world of the '70's by discarding policies based on outdated Cold War assumptions.

Speaking to about 200 people at the Law School Forum, Mathias, a young liberal Republican, explained a resolution he is proposing that would revoke some of these policies and return foreign policy powers to the Congress.

The resolution, co-sponsored by Senate Majority Leader Michael J. Mansfield (D-Mont.), would repeal four "Cold War" resolutions-including the Tonkin Gulf Resolution. Mansfield and Mathias testified in favor of the proposal before the Senate Foreign Relations Committee last week.

The proposal, which has not yet been reported out of committee, calls for the "accelerated withdrawal of American troops" from Vietnam and aims to restrict the emergency powers of the President.

Mathias said last night that such Cold War myths as the existence of a communist conspiracy are too outmoded to be implicitly retained in policies. "An automatic anti-Communist policy will isolate us more surely from a world in constant change-the world of the '70's-than any deliberate isolationism that could be adopted," he added.

Although the resolution would specifically remove powers from the Presidency and restore Congress's war-making prerogatives, Mathias said that he did not want to "pull the fangs of the President in all foreign policy matters."