President Donald Trump was sued again over his plan to ban transgender Americans from serving in the military, setting the stage for another bruising court battle about 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.

The ACLU’s suit seeks a preliminary or permanent court order barring enforcement of the ban and preventing any transgender service members from being discharged, blocked from promotion or denied medical care.

Trump ordered the military to stop paying for transition-related medical expenses, unless the service members’ health was in jeopardy, and the ACLU asked the judge to reverse that order immediately. It’ll be up to the judge to schedule hearings.

The ban is “purely political,” the ACLU said, “reflecting a desire to placate legislators and advisers who bear animus and moral disapproval toward men and woman who are transgender in order to gain votes to pass a defense-spending bill that included money to build a border wall with Mexico.” Another suit filed Monday in federal court in Seattle by Lambda Legal said Trump’s policy was “unsupported by any compelling, important, or even rational justification.”

The dispute was triggered by a three-part July 26 tweet in which the president said he needed to reverse his predecessor’s transgender policy to protect military readiness and reduce waste.

“After consultation with my Generals and military experts, please be advised that the United States Government will not accept or allow Transgender individuals to serve in any capacity in the U.S. Military,” Trump tweeted. “Our military must be focused on the decisive and overwhelming victory and cannot be burdened with the tremendous medical costs and disruption that transgender in the military would entail. Thank you.”

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The ACLU’s complaint purports to address each of Trump’s stated concerns, using government-backed studies, an analysis of transgender-related costs and the apparent readiness of several U.S. allies that allow transgender soldiers to serve openly. Moreover, the civil rights group says, it’s a constitutional matter.

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.

“We do not comment on active or pending litigation,” Ninio Fetalvo, a White House spokesman, said in an email.

The plaintiffs in the suit include Petty Officer Brock Stone, 34, who has served in the U.S. Navy for 11 years, including a nine-month deployment to Afghanistan, and Staff Sgt. Kate Cole, 27, who has served in the U.S. Army for almost 10 years, including a year in Afghanistan where she was a team leader and designated marksman.

The Department of Defense concluded in 2016 that there was no basis for the military to exclude transgender men and women from serving openly, subject to the same fitness requirements as other Americans, the ACLU said. New transgender recruits were due to be permitted to enlist on July 1, it said.

The ACLU has also helped stall Trump’s proposed ban against travelers from several Muslim-majority countries, a narrowed version of which took effect in June pending a U.S. Supreme Court hearing in October.

Thousands of transgender Americans serve in the armed forces, putting themselves in harm’s way to protect the rights and freedoms in the U.S., the ACLU said in the complaint.

“Some perform critical roles in intelligence analysis, disaster relief, medical care, and predeployment training at bases in the United States,” the organization said. “Others have deployed to combat zones in Iraq and Afghanistan.”

Trump’s claim that allowing transgender Americans to serve openly would harm unit cohesion is undermined by the experiences of soldiers in 18 countries were they’re allowed to serve, including Canada, Australia, Germany and Israel, the suit says. That was the conclusion of a RAND Corporation study that investigated the matter for the Obama administration, according to the ACLU.

The suit quoted Sen. Tammy Duckworth, D-Illinois, an Iraq War veteran and a recipient of the Purple Heart, criticizing Trump’s planned policy in a statement.

“If you are willing to risk your life for your country and you can do the job, you should be able to serve — no matter your gender identity or sexual orientation,” she said.

The suit also disputes Trump’s claim that proving medical treatment for transgender men and women is too costly. The group cited a study showing an projected increase in spending of $8.4 million out of a $6.2 billion budget, according to the suit. The military spends ten times that amount — $84 million annually — providing Viagra and sexual dysfunction medications to members of the armed forces.

Treatment of transgender people has become a flash point as social conservatives lead fights in some states to require students and sometimes adults to use schools and public restrooms corresponding to their gender at birth.

Five members of the armed forces earlier this month sued Trump and his top military brass seeking to halt the reversal of the transgender policy put in place by the Obama administration. The new suit by the ACLU adds significant resources to the fight as the organization has seen its membership swell since Trump’s election.

The service members in the earlier case, who are suing anonymously, say they disclosed their gender orientation relying on the existing policy that permits them to serve openly.