President Trump will likely find himself in court over his Tuesday night decision to allow 15-percent ethanol fuel be sold year-round across the nation, according to the refinery industry's top lobbyist.

“The President’s proposal to waive the rules for E15 is unlawful and could actually make the problems of the Renewable Fuel Standard worse," Chet Thompson, president and CEO of the American Fuel and Petrochemical Manufacturers, said in a statement.

A source close to the refinery group told the Washington Examiner that it is "likely" the group will sue the administration for going ahead with the plan.

Thompson, in an interview with Reuters, had said that the "only certainty from today’s actions is a lawsuit.”

Trump announced from Iowa Tuesday night that he would be allowing E15 to be sold year-round, instead of just 8 months of the year because of EPA rules governing fuel volatility and pressure ratings. Waiving the restrictions would open up a new market for corn farmers and Iowa's ethanol producers.

Thompson had joined with the oil industry last week in prodding Trump in a letter not to move forward with the plan because of the harmful effects E15 could pose on consumer vehicles.

But instead, Trump's moving forward with the plan reneges on a promise to reform the Environmental Protection Agency's renewable fuel program, Thompson added

"The President has promised to broker a deal to reform the RFS that works for all stakeholders. This isn’t it," Thompson said.

"We are disappointed to see that despite good-faith efforts by refiners to find potential solutions, the Administration has unilaterally embraced a one-sided approach that only serves the ethanol community, which has shown little interest in finding common ground," Thompson said.

He urged the president and EPA Acting Administrator Andrew Wheeler "to abandon this ill-conceived idea and instead take meaningful action that addresses the real problems with the RFS.”

Although Trump's plan also included actions to fix the ethanol credit trading system to help refiners deal with the cost of the renewable fuel program, it doesn't seem to be enough for Thompson's group, which represents the nation's top refining companies.

The oil and refinery industries see the EPA ethanol program as a failure, requiring either significant reforms by Congress or repeal.