UNTIL recently, one or more players in the Arab-Israeli conflict rejected United Nations Resolution 242 for one reason or the other. By the time the Palestine Liberation Organization (PLO) accepted 242 in December 1988, the Israeli government under Yitzhak Shamir rejected any further territorial concessions. The election of Yitzhak Rabin in Israel last June finally restored, after 25 years, Resolution 242 as the main instrument of reference for all future Arab-Israeli negotiations.
Even though many aspects are ambiguous, Resolution 242 established the principles on which an Arab-Israeli peace can be erected. The test for the Arab and Israeli representatives meeting this week in Washington for another round of talks is whether they find strength in the resolution's ambiguities and continue with the negotiating process until peace is achieved.
After Resolution 242 was adopted in 1967, the Arab states and the Palestinians made repeated attempts to incorporate into it a recognition of the Palestinians' right to self-determination. In explaining its 1976 veto of a draft resolution that would have changed the framework of 242, the United States asserted that "whatever its imperfections and however great the temptation to tamper with the resolution, there would be no chance for further progress if this negotiating framework, painfully erected over years of trial and error, was not left intact."
The Egyptian-Israeli peace treaty and the Camp David accords, which include a formula for Palestinian self-determination, were based on 242. Arab rejection of the accords and Likud resistance to further territorial concessions, however, increased the diverse interpretations of the resolution's most important provisions regarding the exchange of territory for peace.
SUCCESSIVE Likud governments maintained that Israel had already fulfilled the resolution's provisions calling for "withdrawal of Israel's armed forces from territories occupied in the  conflict." That requirement was met, Likud officials insisted, when Israel evacuated the Sinai (which represents 92 percent of the land captured) and returned it to Egypt in 1979 as part of the Camp David accords.
Another point of contention developed around the interpretation of the phrase, "to live in peace within recognized and secured borders." From the Likud's vantage point, this provision authorizes the retention of the West Bank and the Golan Heights as essential to Israeli security. In addition, Likud officials argued vehemently, Resolution 242 did not call for the withdrawal from "the territories," but only from "territories."
Prime Minister Rabin's interpretation is closer to that of the US, which left the extent of the territorial withdrawal to be decided in the negotiations as long as the withdrawal is on all fronts. The Arab states insist that Israel should withdraw from all territories captured on all fronts and that the reference in the resolution to secure borders implies only minor border adjustments that may be necessary to maintain Israel's security.
Probably the most critical point of contention is the provision that calls for the "achieving a just settlement of the refugee problem." While it has been universally accepted that the Palestinian question is more than a refugee problem, including also the issue of national identity, both Labor and Likud agree that the resolution was deliberately worded to preclude self-determination (a euphemism for a Palestinian state).
Like Mr. Shamir, Rabin says a Palestinian state already exists - Jordan. Palestinian national aspirations must be met, he contends, in the context of a Jordanian-Palestinian solution. Resolution 242 was intended to achieve a "just and lasting peace in which every state in the area can live securely." Israel insists that the authors of 242 envisioned a solution to the Palestinian problem among the existing states, with territorial adjustments.
However objectionable the antagonists may find some of the provisions of Resolution 242, after 25 years it remains the only instrument that offers both the flexibility and a fair basis needed for negotiations - despite, or because of, flaws resulting from its ambiguities. In this respect the resolution remains indispensable.