If you want to deter your relatives from marrying out, then one way is to disinherit them if they do.

But would it be legal? That is precisely the issue that is being thrashed out in the American courts.

When Chicago dentist Max Feinberg died in 1986, he left a clause in his will stating that any of his descendants - other than his two children -who married out should be considered "deceased" if they married a non-Jew, unless the spouse converted to Judaism "within one year of marriage".

But the terms of his will have led to a dispute between one of his five grandchildren, Michele Trull, who wants to overturn the so-called "Jewish clause", and her father, Michael Feinberg, and aunt, Leila Taylor, who have fought to uphold it.

Ms Trull, who along with three of the other grandchildren has a non-Jewish spouse, stands to gain $250,000 (£125,000) if the courts support her. The money seemed within reach earlier this summer when the Illinois Appeal Court delivered a verdict by two-to-one in her favour.

Justice Joy Cunningham stated that the condition was "invalid because it interferes with and limits the right of individuals to marry a person of their own choosing".

But Ms Trull's father, Michael Feinberg, a retired dentist, has since petitioned the state's Supreme Court to reinstate his father's wishes.

The legal wrangling began after the death of Max's widow, Erla, in 2003: Ms Trull has alleged that the co-executors of her grandparents' estates - including her father and aunt - misappropriated millions of dollars.