Massachusetts Attorney General Maura Healey [official website] filed an amicus curiae brief [text, PDF] Monday in support of a lawsuit challenging President Donald Trump’s directive [text] to reinstate a ban on transgender individuals openly serving in the military.

Joining Massachusetts in the brief are California, Connecticut, Delaware, Hawaii, Illinois, Iowa, Maryland, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont and the District of Columbia.

Calling the ban “unconstitutional, unjustified and discriminatory” and noting that the states share a strong interest in the “readiness and effectiveness of our national defense, including an interest in ensuring that our Armed Forces and related institutions recruit, train, retain, and promote qualified service members,” the brief argues that:

States have enacted and enforce explicit civil rights protections for transgender people in areas such as employment, housing, health care, education, and public accommodations. We also command National Guard units, support Reserve Officer Training Corps programs, and run maritime academies that embrace principles of nondiscrimination and equality. Our collective experience demonstrates that the full inclusion of transgender people strengthens our communities, our state and federal institutions, and our nation as a whole. Discriminatory prohibitions on participation in civic life, on the other hand, impose significant harms on the Amici States and our residents. The Amici States therefore have a strong interest in ensuring that our Armed Forces move forward, not backward, and continue to allow transgender people to serve openly in all branches. … The military has already concluded that allowing transgender individuals to serve openly is in the nation’s best interest.

Trump issued [JURIST report] a memorandum directing the Secretaries of the Departments of Defense and Homeland Security [official websites] to reinstate the ban in August, after he announced the reversal in policy in a series of tweets the previous month. The ban against transgender individuals serving in the military is a longstanding policy that had been operative through most of former president Barrack Obama’s presidency until his administration lifted [JURIST report] it in 2015.

This suit was brought by five unnamed individuals alleging that re-imposition of the ban would violate the Due Process and Equal Protection clauses of the Fifth Amendment of the US Constitution. The suit seeks a preliminary injunction against implementation of the ban and this brief has been filed in support of the same. According to the brief, approximately 150,000 veterans, service members and National Guard members currently identify as transgender, and transgender individuals volunteer to serve at twice the rate of the US adult population.