The state’s chief judge on Wednesday announced the details of a new rule — the first of its kind in the nation — requiring law students to perform 50 hours of unpaid work as a condition of practicing in New York.

The rule requires law students to do pro bono work for the poor, nonprofit or civil rights groups or any of the three branches of government, between the first year of law school and the time they apply for a license. The work can be performed anywhere in the world but students must be under the supervision of a practicing lawyer, a judge or a member of a law school faculty. The law goes into effect for new students in law schools on Jan. 1.

When the judge, Jonathan Lippman, proposed the rule in May, some in the legal community said it might be burdensome for new lawyers in a tough economy. Others voiced concerns about using those new to the profession to fill what Judge Lippman calls the justice gap: the growing number of people who cannot afford legal services.