The president earlier refused to sign it until a divisive voting-rights measure was passed.
Markwayne Mullins’ comments came after the Supreme Court allowed the Trump administration to strip hundreds of thousands of Haitians and Syrians of their protected status.
The U.S. Supreme Court is expected to wrap up its current term in the coming days, with several major cases yet to be decided, including three involving Donald Trump’s far-reaching assertion of presidential powers, two important election-related cases and one involving a crackdown by states on transgender athletes.