EGYPT'S recent return to the Islamic Conference Organization is cause of mixed feelings. Egypt, for so long ostracized and vilified in the Muslim and Arab worlds because it made peace with Israel, is now welcomed back to the Islamic fold without having to formally renounce its treaty with Israel. This rapprochement appears to reflect a desire to forge a coalition of supposedly moderate Arab states. Its presumed object: to resist the expansionism and subversion of the alliance between Soviet-backed Syria and Libya and the revolutionary Islamic crusade led by Khomeini.
This policy bears a major flaw: It is undertaken at the expense of Israel. Tragically, in this respect, the ''moderates'' and the radicals are equally immoderate: Rejection of Israel turns out to be the only unifier of the otherwise bellicose ''fraternity'' of the Islamic world.
Disquiet on this score is aroused by a statement attributed to Egypt's President Mubarak by Morocco's King Hassan II at the Islamic Conference summit in Casablanca just two weeks ago: ''Camp David remains alive only in the minds of the Arabs. In our country, in Egypt, it is drained of its substance, because Egypt obtained, thanks to Camp David, what it wanted.''
This statement figured prominently on Jan. 21 and remained unrepudiated until Feb. 15 when questioned by a Washington Post reporter. Then Mubarak denied the attibution. Such a denial will hardly penetrate the consciousness of the Arab and Muslim worlds. All this must give rise to grave misgivings, for it caps a series of wide ranging Egyptian violations of the Camp David Accords and the peace treaty.
* Egypt's ambassador to Israel has now been withdrawn for a year and a half, despite assurances of his return given last spring to Israel and the United States.
* There has been no relaxation of trade restrictions, despite undertakings given to Israel last March. Since early 1983 the issuance of letters of credit for Israeli exports to Egypt has been made harder. In June 1983, Egypt stopped issuing import licenses for Israeli goods.
* Egypt complies with much of the Arab boycott of Israel. The public sector, comprising about 80 percent of the Egyptian economy, remains closed to Israeli business. The Egyptian National Shipping Company, which controls the bulk of shipping to Egypt, refuses to recognize Israeli shipping companies as authorized carriers on its behalf. Israel has been prevented from participating in three major fairs in Egypt: the Cairo Agriculture Fair in October 1982, and the two Cairo Book Fairs of January 1983 and 1984.
* Egyptian tourism to Israel is actively discouraged and impeded by administrative and bureaucratic obstructionism. Even at the best of times, only a trickle of Egyptian tourists came to Israel, while some 100,000 Israelis have visited Egypt.
* All cultural exchanges have been halted by Egypt.
* In the Sinai, Egypt has overlooked certain security provisions and a military infrastructure beyond the prescribed limits has been constructed.
* Crude anti-Semitic propaganda against Israel and the Jewish people in general has appeared regularly in the mainstream Egyptian press and has been frequently used by Egyptian spokesmen at various UN bodies.
* It is important to note that President Murbarak announced that Egypt was rejoining the Muslim organization ''within the framework of the Islamic Conference's charter, to which it had always been committed.'' The charter has as its fundamental aim ''support of the struggle of the Palestinian people,'' and the conference has played a significant role in rallying worldwide Muslim hostility against Israel.
''For Egypt, Camp David is dead.'' With this ominous declaration, King Hassan persuaded the conference that Egypt's peace treaty with Israel should no longer be regarded as the main stumbling block in the way of Cairo's readmittance to the organization.
''This is so,'' he continued, ''because it has obtained all its fruits, Egypt has recovered its occupied territories. It recovered its petroleum. Because of this, the substance of Camp David has been drained.
''Formally, the treaty remains. It is difficult, of course, to tear up treaties. . . . Nevertheless, in politics, there is not only form but also substance.''
This declaration bespeaks a shocking cynical opportunism that bodes ill for genuine peace. One must fervently hope that it has not become Egypt's policy.