Republican senator Thom Tillis said the sanctions relief on Russian diesel could violate congressional law, in a Sunday interview on NBC News’s Meet the Press, according to Al Jazeera.

“I do believe there’s a legitimate case for saying the president’s not following the law,” Tillis said. A bipartisan group of senators called for an immediate reversal of the relief, saying the United States should not provide Vladimir Putin with a financial lifeline while Russia continues to kill Ukrainian civilians.