The Orthodox religious establishment has only itself to blame for the Israeli Supreme Court’s decision last Thursday validating, for the purpose of recognition by Israel’s “Law of Return,” Reform and Conservative conversions to Judaism undergone by Israeli residents outside of Israel.

The court, to be sure, did not take the final step of accepting such conversions when performed in Israel itself. As of now, would-be converts still do not have the option of taking the Reform or Conservative route to Jewishness in Jerusalem or Tel Aviv, where Orthodox conversions alone remain recognized. Yet the way is now open for them to study in Israel with non-Orthodox rabbis and then fly to New York or London to have a valid conversion performed.

Moreover, the court’s decision may be transitional in nature. In dealing with new appeals that are in the offing, it is likely to extend its ruling to in-Israel conversions, too, before the retirement in 2006 of Chief Justice Aharon Barak, the driving force behind its liberal activism. This would be in keeping with a slow but steady judicial widening of Reform and Conservative prerogatives that began in 1986 with the Shoshanna Miller case, in which Israel’s high court mandated applying the Law of Return to non-Orthodox converts who were not Israeli residents when they converted.

The Orthodox reaction to last Thursday’s verdict has been expectedly fierce. Nor is it entirely without substance. Letting a non-Orthodox conversion determine eligibility for the Law of Return, which automatically grants Israeli citizenship to any Jews, has its dangers.

These are obvious. An Orthodox conversion is difficult. It involves many long months of study, frequent questioning by one’s religious mentor, constant examination of one’s motives, tangible indications that one means to live a Jewish life. Few people who do not sincerely want to become Jewish would bother to do so in so arduous a manner.

There is no need to make light of either Conservative or Reform Judaism in order to concede that their conversions are far easier. Even if these aren’t of the “quickie” variety that can be completed in a few days, they demand considerably less effort and dedication. For someone merely looking for Israeli citizenship, becoming Jewish via non-Orthodox channels is a not unreasonable investment of time.

One needn’t worry about this happening, of course, with Western Europeans or Americans. No one is going to convert to Judaism, however effortlessly, in order to gain the right to live in a country with a lower standard of living and a more pressured existence than he is used to. Israel is not about to be deluged by immigrants from France or England brandishing quickie conversions.

The problem is with Second and Third World immigrants. Already today, Israel is host to legions of foreign workers, legal and illegal arrivals from China, Thailand, the Philippines, Ghana, Nigeria, Ecuador, Colombia, Rumania, Ukraine, and a dozen other places. Although their number has dropped sharply over the past two years because of an aggressive campaign to deport those without visas, it still may be as high as 200,000.

Most of these people are in Israel for economic motives having nothing to do with Jewishness and most would gladly remain. The Supreme Court’s decision now allows any of them, in principle, to fly abroad for a long weekend, find a non-Orthodox rabbi to convert them, and fly back to Israel to file for citizenship. It also reinforces the Miller decision, which would allow unlimited numbers of foreign workers to enter Israel as Jews by obtaining easy conversions first.

This entire complication might have been avoided had the Orthodox rabbinate in Israel been, over the years, more forthcoming in its attitude toward prospective converts and less inhospitable toward them. Orthodox conversions in Israel have been notoriously difficult to obtain and the rabbinical courts have frequently treated those seeking them more as suspected interlopers than as welcome additions to the Jewish people.

Many prospective converts have given up after having their good faith repeatedly questioned; many more have been scared off from trying. Apart from the foreign worker community and Israel’s Arab minority, there are today in Israel large numbers of non-Jews, mostly Gentiles from the ex-Soviet Union married to or the descendants of Jews, who have refrained from becoming Jewish solely because of the unpleasantness involved.

Had the process of Orthodox conversion in Israel been reasonably challenging, instead of dauntingly forbidding, the Supreme Court might have thought twice about putting its stamp of approval on problematic non-Orthodox alternatives.

As it was, it clearly felt that would-be converts deserved a faster lane. On the Conservative and Reform movements in the Diaspora now rests the responsibility to see to it that this ruling is not abused. It is one thing, after all, for a non-Orthodox rabbi to perform a quick conversion that enables someone to marry in a Jewish ceremony or join a local synagogue; it is another to hand over, in effect, the keys to Israeli citizenship. A greater degree of supervision of converting Conservative and Reform rabbis may now be called for.

Eventually, Israel will have to find more radical solutions than those offered by anachronistic religious criteria to the perennially vexing question of who is a Jew according to Israeli law. Neither Israel nor the Jewish people have fully come to terms with the Zionist revolution that created a Jewish state and transformed Jewish identity within its boundaries from a religious and ethnic category to a national one. Yet these solutions will demand such new ways of thinking, for which neither Israeli nor Diaspora Jews are yet prepared, that there is meanwhile a strong preference for limited tinkering with the old ways. As tinkering goes, the Supreme Court’s decision is a step in the right direction.

Mr. Halkin is a contributing editor of The New York Sun.