It is hard to see any resemblance between S. 1203, the Anti-Terrorism Act of 1987 (which would ban the PLO from expending any monies in this country or operating an office here), and the bill The Post criticizes in its editorial {"Closing PLO Offices," May 26} on the ground that the bill would abridge freedom of speech.

The bill would not, in fact, outlaw speech in any way. By explicit provision of the act, the PLO itself (which as a foreign entity, it has been held by the Supreme Court, enjoys no constitutional rights) may distribute any form of informational material in the United States. Any American may become a member of the PLO and communicate with it in any lawful manner.

Under the act, any American would be free to endorse the PLO or its political views. One could, without in any way being in violation of the proposed act, argue, for example, that the PLO is justified in murdering innocent men, women and children, blowing up airplanes or hijacking a ship and tossing a crippled American citizen overboard. And one would be free, under the act, to communicate such a view to others. Such activities are plainly protected by the First Amendment and would in no way be restricted by the Anti-Terrorism Act of 1987.

What the bill does regulate is conduct -- the operation of an office -- and conduct plainly within the reach of Congress. What it seeks to deny to the PLO is the political prestige it gains from maintaining offices in this country -- until such time as the PLO renounces its practice and support of terrorism. The Anti-Terrorism Act is not an attempt to silence speech, but to condition an important political right -- an official presence in the United States -- on the barest minimum standards of civilized conduct.

The Supreme Court, on at least four occasions, has upheld statutes that limited foreigners' access to Americans. While such statutes, as the court acknowledged, may have some marginal impact on the free flow of information -- that marginal harm is outweighed by the needs of foreign policy. Any interference in the flow of information would be minimal under the Anti-Terrorism Act in any event, since the PLO would be guaranteed the right to distribute any and all informational materials.

The United States has had a consistent and longstanding policy of quarantining the PLO, in an effort to press it to adopt a civilized code of behavior. The First Amendment is not a bar to such a justifiable policy. MARC D. STERN Co-Director Commission on Law and Social Action American Jewish Congress New York