Israel’s Supreme Court decided by a vote of 10 to 1 to reject Shas Party Chairman Aryeh Deri’s ability to serve as a cabinet member in the Netanyahu government, arguing on Wednesday that Deri’s ministerial appointments were unreasonable in the “extreme.”

Deri serves as interior and health minister in the new government. He is also vice prime minister.

“The Supreme Court threw into the trash the votes of 400,000 voters,” the Shas Party said in a statement.

The court issued the ruling despite a Knesset amendment passed in December to allow Deri to serve as a minister. The amendment specified that a ban on persons serving as ministers for seven years if convicted of a criminal offense applies only to those serving active jail sentences. Deri was handed a suspended jail sentence as part of a plea bargain on tax fraud in February of last year, and so it had been unclear whether the ban applied to him.

The court’s decision could create government instability.

Shas Party member Ya’akov Margi, the minister of labor, social affairs and social services, warned in a Channel 11 interview on Wednesday just prior to the court’s announcement that Prime Minister Benjamin Netanyahu “knows that if Aryeh Deri is not in the government, there is no government.”

Similarly, in an earlier response to the petitions against Deri, Netanyahu and his Likud Party said, “There is no way to bring about governmental stability without the appointment of Shas leader Aryeh Deri as minister. Shas is the second-largest faction in the coalition. Ignoring the clear will of the voters would constitute clearly unreasonable behavior.”

The Shas Party won 11 Knesset seats in the November election.

Opposition leader Yair Lapid said on Wednesday, “If Aryeh Deri is not fired [by Netanyahu], the Israeli government is breaking the law. A government that does not obey the law is an illegal government. It can no longer demand that citizens obey the law.

“If Aryeh Deri is not fired, Israel will find itself in an unprecedented constitutional crisis and it will no longer be a democracy,” he added.

For his part, Justice Minister Yariv Levin called the court’s decision “absurd,” saying it “tramples over the votes not only of nearly 400,000 Shas voters, but also the will of the majority of Israeli citizens who knew the facts and voted for a government led by Netanyahu in which Aryeh Deri would be a senior partner.”

Levin added that would “do everything to repair the terrible injustice done to Israeli democracy.”

His comments were echoed by Knesset Speaker Amir Ohana, who said the court does not have jurisdiction to intervene and that “now the legislative branch will have its say.”

The Deri decision against the background of a political battle around the Netanyahu government’s judicial reform plan, which aims to curtail what it says is judicial overreach. The plan would give the Knesset the ability to overturn court decisions that cancel laws, allow elected officials greater influence in selecting judges, and reduce the power of legal advisers attached to government ministries.

In what reform advocates point to as a prime example of the latter, the government’s chief legal adviser, Attorney General Gali Baharav-Miara, refused to represent the government in the Deri case, basically siding with the prosecution. She allowed the government to hire outside counsel.