Some years ago, a woman who had completed an Israeli Orthodox conversion course finalised her conversion to Judaism on a Friday morning by immersing in a mikveh and accepting the commandments in front of a rabbinical court. Hours later, she boarded a plane for Turkey and by Saturday morning, she and her non-Jewish boyfriend were married in a civil ceremony in Istanbul.

On Sunday morning, the new couple approached the immigration desk at Ben Gurion airport seeking to make aliyah —she on the basis of her conversion, and he as a spouse of a Jew.

I present this narrative to indicate that even as a strong advocate of conversion rights and someone who has fought hard against the annulment of conversions, I recognise that fraudulent behaviour — especially in conversion — must be held in check. I cannot accept that someone who declares fealty to a halachic lifestyle could blatantly violate the Shabbat hours later, and then intermarry on the morrow.

But even as I recognise the challenges of determining integrity when it comes to conversion, the approach adopted by the recent Israeli legal brief, which argues that all conversions are to be held in check in perpetuity, is equally scandalous and disingenuous.

As reported, the central claim of the brief —that the subsequent behaviour of a convert casts aspersions upon the integrity of the conversion process and particularly the acceptance of mitzvot — is flawed on three counts and unprecedented in its scope. On the most basic plane, it contradicts the Talmudic prescription that states explicitly that a convert who returns to “his ways” is considered fully Jewish. The brief represents a radical interpretation of sources and a twisting of rabbinic literature.

Secondly, the brief provides no basis for what is known in the legal world as a sunset provision. According to reports, the legal position does not differentiate between subsequent behaviour in the hours following a conversion and in the decades following a conversion. Nor does it offer a prescription for who can determine whether a convert has really “left the path”.

But it is the final count that is most disturbing. The brief opens a Pandora’s box for converts around the world. The Torah declares some 36 times how sensitive the Jew must be to the convert, particularly because of the convert’s vulnerability. If the court adopts the position advocated in the brief, no convert is safe, and no convert is protected. In the past two weeks, converts around the world have called my office concerned about their future. Is this not persecution of the weak and defenceless?

And so, even as I recognise that fraud must be eradicated, I feel strongly that challenging converts who finished the process on their present behaviour is tantamount to harassment. Before we begin to challenge the other, we need to look deeply into our own motivations, and ensure that along the way, way haven’t lost track of our values.

Rabbi Seth Farber is founder and director of ITIM: The Jewish Life Information Centre (www.itim.org.il) and rabbi of Kehillat Netivot in Raanana