NEW YORK (AP) — Donald Trump is naming longtime adviser Stephen Miller, an immigration hard-liner, to be the deputy chief of policy in his new administration.

Vice President-elect JD Vance posted a message of congratulations on Monday to Miller on X and said, “This is another fantastic pick by the president.” The announcement was first reported by CNN.

Miller was a senior adviser in Trump’s first term and has been a central figure in many of his policy decisions, notably his move to separate thousands of immigrant families as a deterrence program in 2018. Miller helped craft many of Trump’s hard-line speeches and plans on immigration.

Since Trump left office, Miller has served as the president of America First Legal, an organization of former Trump advisers fashioned as a conservative version of the American Civil Liberties Union, challenging the Biden administration, media companies, universities and others over issues such as freedom of speech and religion and national security.