Sen. Chuck Grassley is warning the White House that it cannot legally appoint Ken Cuccinelli to lead the Department of Homeland Security.

President Trump is seeking an end-around to appoint the immigration hardliner to the position, and Cuccinelli is loathed by Senate Majority Leader Mitch McConnell (R-Ky.) and other Republicans to the point that he probably could not be confirmed. And Grassley, the most senior Republican, said there is no legal way to put the acting U.S. Citizenship and Immigration Services chief in the position as acting chief after acting DHS Secretary Kevin McAleenan leaves his post on Thursday.

“There’s some opposition to Senate confirmation. I have not heard anything about some go-around. But it’s my understanding that the existing law would not permit him to” lead the organization, Grassley said in an interview. “I don’t know how you get around that. I don’t think it’s possible because of what the law says, not because of anything else.”

House Homeland Security Chairman Bennie Thompson (D-Miss.) called on the Trump administration to disavow reports that Cuccinelli may be elevated.

“If the White House cannot find anyone qualified and suitable to run the Department of Homeland Security - or even run it in an acting capacity - something is very wrong with this Administration,” Thompson said on Wednesday morning.

Grassley suggested that acting undersecretary Chad Wolf, who has been nominated to be a permanent position, could be confirmed and take the acting job atop DHS. But it’s unclear that confirmation could happen quickly enough and Grassley said he had no inside information that Wolf will be Trump's pick.

The New York Times first reported the effort to appoint Cuccinelli.