A federal judge on Monday struck down a $100,000 fee U.S. President Donald Trump imposed on new H-1B visas for highly skilled foreign workers, concluding that it constituted an unlawful ​tax Congress never authorized.

U.S. District Judge Leo Sorokin in Boston issued the ruling in a lawsuit filed ‌by 20 Democratic state attorneys general challenging a fee Trump announced in September that dramatically raised the cost of obtaining H-1B visas.

The administration argued the fee constituted a lawful monetary penalty that the president was authorized to impose under federal immigration law, which gives him the power ​to restrict the entry of certain foreign nationals when he deems it “detrimental to the interests of the United States.”

But ​Sorokin concluded that the fee was not a penalty but a tax that the Republican ⁠president lacked any authorization from Congress to issue and that the U.S. State Department and U.S. Citizenship and Immigration Services ​could not implement.

“Here, the substance and application of the $100,000 payment reveal that it is a tax, regardless of what the ​payment is called,” wrote Sorokin, who was appointed by Democratic President Barack Obama.

The judge cited the U.S. Supreme Court’s February ruling striking down Trump’s sweeping tariffs he pursued under a law meant for use in national emergencies. Under the logic of the justices’ decision in that case, Trump similarly ​had no authority under immigration law to levy a tax, Sorokin said.

White House spokeswoman Taylor Rogers in a statement said ​the Trump administration is confident Sorokin’s order will be reversed on appeal.

“President Trump has clear legal authority to restrict entry of any ‌class of ⁠aliens he determines is not in America’s best interests, and that is exactly what he did,” she said.

The H-1B program offers 65,000 visas annually, with another 20,000 visas for workers with advanced degrees, approved for three to six years. Technology companies in particular rely heavily on workers who receive H-1B visas.

Employers seeking a visa for a foreign worker before Trump’s proclamation typically ​paid about $2,000 to $5,000 in fees ​depending on various factors. The ⁠fee will not apply to visas granted to foreign citizens already in the United States on student visas, who generally make up a large share of new H-1B recipients.

The increase ​in fees has discouraged H-1B visa requests, according to court filings. As of February 15, ​U.S. Citizenship and ⁠Immigration Services had received just 85 payments of the $100,000 fee, the administration said in a March filing.

The Trump administration has also ordered enhanced vetting of H-1B applicants and proposed a new visa selection process that would favor higher-skilled and better-paid workers.

The $100,000 fee prompted ⁠at least ​three different lawsuits challenging its implementation, including a case by the U.S. ​Chamber of Commerce, which is appealing a December decision by a judge in Washington, D.C., who rejected its claims that Trump had no authority to set ​the fee.