Israel’s Supreme Court ruled Wednesday that Prime Minister Benjamin Netanyahu must fire a key ally from the country’s new Cabinet, presenting the Israeli leader with a potential coalition crisis and deepening a rift over the power of the courts.

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. Deri has pledged not to quit and met after the ruling with Netanyahu.

“Most of the judges on the panel decided that this appointment suffers from extreme unreasonability, and therefore the prime minister must remove Deri from his position,” the court said in a statement.

The much-anticipated ruling comes as Israel is being roiled by a dispute over sweeping changes to the country’s legal system. One such proposal under consideration is the elimination of the court’s “reasonability” test when reviewing government decisions.

Critics say the various changes at issue would place too much power in the hands of the government and weaken the Supreme Court. Proponents say they would correct a power imbalance between the executive and judicial branches.

Netanyahu will now have to decide whether he abides by the court ruling and fires his key ally, Deri — or takes the dispute with the judicial system up a notch and defies it. A spokesman for Netanyahu had no immediate comment.

But the leaders of the parties in the ruling coalition decried the ruling as a slap at voters after the Nov. 1 election. In a statement, they vowed to act “in any legal way that is available to us and without delay to correct the injustice and the severe damage caused to the democratic choice and the sovereignty of the people.(asterisk)

Dr. Amir Fuchs, senior researcher at the Israel Democracy Institute, said Netanyahu is unlikely to ignore the ruling because then he’d be in contempt of court and there is no appealing a Supreme Court decision.

“I am sure that he will abide by the ruling. It doesn’t mean that he will respect the ruling,” Fuchs said. “What will probably happen is that they will do very quick legislation that will enable him to appoint Deri again.”

It’s not clear whether the proposed legal changes, including a plan to allow lawmakers to overrule Supreme Court decisions, could retroactively be applied to Deri’s case.

Critics said such a move would bend the rules to accommodate a convict and could encourage corruption among politicians.

The ruling carries potentially troublesome consequences for Netanyahu’s coalition. Some Shas members have urged Netanyahu to find a solution that would grant Deri the title they say he deserves as head of a mid-sized party. Otherwise, the party could bolt the coalition, which would shrink Netanyahu’s 64-seat majority by 11 seats in the 120-member Knesset.

Yakov Margi, a Shas Cabinet minister, told Kan public radio that, “if Aryeh Deri isn’t in the government, there isn’t a government.”

In a move that was seen as crucial to bringing the governing coalition together, Israeli legislators last month changed a law that prohibited a convict on probation from being a Cabinet minister. That cleared the way for Deri to join the government but prompted the Supreme Court challenge.

Deri is currently serving half a term as the minister of health and interior affairs. He was set to become finance minister in the second half of the term and he is also deputy prime minister.

Likud and its ultra-Orthodox and far-right partners captured a majority of seats in the Knesset, or parliament, in Nov. 1 elections, and formed a government that has made changing the legal system a centerpiece of its agenda.

Public opinion polls have shown most Israelis oppose Deri serving as a government minister.

Still, the Deri ruling is only expected to deepen the divide over the legal overhaul. It will be seen by both camps as an affirmation of their views: either that the courts, in determining who can be a Cabinet minister, have too much power, or that judicial oversight can hold back legislators from questionable laws.

“Today it’s clear that the court, which is not elected, is not interested in compromises and wants limitless control over elected officials,” National Security Minister Itamar Ben-Gvir said in a statement. “Reform now!”

Opposition leader Yair Lapid said that if Deri is not fired, “Israel will enter an unprecedented constitutional crisis and it will no longer be a democracy and will not be a law-abiding state.”

In a sign of the charged atmosphere, a Shas member of parliament said before the ruling that if the Supreme Court barred Deri, the justices were “shooting themselves in the head.”

Deri was sentenced to three years in prison for bribery, fraud and breach of trust in 2000 during a stint as interior minister in the 1990s. He served 22 months in prison but made a political comeback and retook the reins of Shas in 2013.