JERUSALEM (AP) — Israel’s Supreme Court ruled Wednesday that a key member of the country’s new government cannot serve as a Cabinet minister. The move deepens a rift over the power of the courts in Israel and presents Prime Minister Benjamin Netanyahu with what could be his first coalition crisis.

The high court ruled that Aryeh Deri, the influential head of the ultra-Orthodox Shas party who has served repeatedly in Netanyahu’s previous governments, is disqualified from serving as a minister after he was convicted last year for tax offenses and placed on probation as part of a plea deal.

The much-anticipated ruling comes as Israel is being roiled by a dispute over sweeping changes to the country’s legal system, which critics say will place too much power in the hands of the government and weaken the Supreme Court. Proponents say it will correct a power imbalance between the executive and judicial branches.