The companies argued in a lawsuit announced on Monday that Biden violated the Constitution by blocking the merger via a sham national security review that deprived the companies of their right to a fair process.

The suit, filed in the U.S. Court of Appeals for the District of Columbia, alleges that it was a political decision and violated the companies’ due process.

President Joe Biden’s decision to reject a bid by Nippon Steel to acquire U.S. Steel isn’t the first time friction over trade and investment has irked Washington’s closest ally in Asia