Rep. Bennie Thompson (D-MS), chairman of the House Committee on Homeland Security, sent a letter to President Donald Trump Monday, saying that his choice of replacement for ousted DHS Secretary Kirstjen Nielsen violates the DHS’ law of succession.

“In announcing Secretary Nielsen’s departure, you tweeted that you plan to install the Commissioner of U.S. Customs and Border Protection as the Acting Secretary,” Thompson wrote. “However, the law of succession at the Department is clear — the Under Secretary for Management shall serve as the Acting Secretary if the Secretary and Deputy Secretary are unavailable.”

“As such, the Under Secretary for Management, Claire M. Grady…is statutorily required to serve as Acting Secretary,” he continued. “I strongly urge you to follow the law in this matter and to nominate a suitable candidate for Secretary as expeditiously as possible.”

Per Politico, Trump may have no recourse but to fire Grady to clear the path for Kevin McAleenan, his preferred candidate.

Read Thompson’s letter here:

