In a letter to the leaders of the American Petroleum Institute, the American Fuel and Petrochemical Manufacturers and the U.S. Chamber of Commerce, the Maryland Democrat said companies that help sell Russian diesel in the United States would be violating federal law. Raskin cautioned that those who proceed could be held accountable “to the fullest extent of the law,” including by a future administration.

The White House disputes that interpretation. A spokesperson said the deal complies with applicable laws, while spokesperson Taylor Rogers accused Democrats of focusing on investigations of Trump rather than improving Americans’ lives.

Raskin, the top Democrat on the House Judiciary Committee, could become its chair if Democrats win control of the House in the November election. He said in the letter that importing Russian diesel could bring penalties of up to 20 years in prison.

The president announced the deal earlier this month, saying it would help lower fuel costs. At the time of the announcement, diesel was reported to cost $2.70 per gallon more than a year earlier. The plan has drawn criticism from lawmakers in both parties, amid concerns about importing fuel subject to U.S. sanctions on Russia.

A cargo of Russian diesel was reported to be en route to the United States and expected to arrive the following week. Democratic lawmakers have also asked port authorities and banks to preserve records related to any shipments, adding scrutiny for businesses that might handle the fuel.

The oil-industry groups and the Chamber of Commerce had not responded to requests for comment by Monday.