JOHANNESBURG — Botswana's courts have nullified a customary law that denied women the right to inherit a family home, a decision seen as a crucial step forward for women's rights in the southern African country.

A judge ruled Friday that the law discriminated against women and was therefore unconstitutional.

The case had been brought by three sisters who want to inherit a family home they have occupied and improved over the years. They faced a challenge from a nephew based on a customary law that gives the youngest-born son the right to inherit the family home.

Priti Patel of the Southern Africa Litigation Centre, which supported the sisters' case, said the decision shows that "the days of women suffering from secondary status under the law in Botswana are drawing to an end."