(Bloomberg) -- U.S. President Donald Trump has been sued again over his plan to ban transgender Americans from serving in the military, setting the stage for another bruising court battle over a directive from the White House.

The lawsuit by the American Civil Liberties Union, filed Monday in federal court in Maryland, alleges Trump’s order violates the Equal Protection clause of the Constitution. An Aug. 25 White House memo gave Defense Secretary James Mattis six months to return to the previous policy barring transgender soldiers and immediately barred transgender-related expenses.

Trump has inflamed U.S. cultural wars since his election victory, pushing back on his predecessor’s liberal polices and pleasing his conservative base. His executive orders have targeted immigration, while his Justice Department started a review of affirmative action in colleges and joined a suit to halt the spread of gay rights in the workplace. The president’s policy proposals have also hinted at fights over abortion and doctor-assisted suicide.