On July 26, 2017, after a series of tweets by President Donald Trump proposing to ban transgender people from military service, thousands of New Yorkers took to the streets in opposition.

The U.S. Supreme Court on Tuesday announced it would permit the Trump administration to enforce a ban on a broad category of transgender troops from serving in the military.

President Donald Trump unveiled the policy in a series of tweets in July 2017, but the new policy was held up by a number of successful legal challenges in federal courts around the country.

In November, the Trump administration asked the Supreme Court to review those lower court decisions and allow the ban to take effect.

The justices said they will not review the policy now, but in an order on Tuesday, the court temporarily lifted injunctions preventing the government from enforcing the ban as it defends it in court. The administration will be allowed to enforce the ban until ongoing litigation in the U.S. 9th Circuit Court of Appeals is resolved.

The court's Tuesday decision was opposed by the four justices of the court's liberal wing: Justices Ruth Bader Ginsburg, Sonia Sotomayor, Stephen Breyer and Elena Kagan.

The troop ban was outlined in detail by then-Secretary of Defense James Mattis in a Feb. 18 memorandum.

Mattis wrote that after conducting a review of the matter, he recommended barring any transgender individuals who had undergone gender transition and, with some exceptions, those who had been diagnosed with "gender dysphoria," or who do not identify with the gender they were assigned at birth.

The ban was blocked by three federal judges who issued injunctions enjoining the military from implementing it. Advocacy groups including GLAD, or GLBTQ Legal Advocates & Defenders, argued successfully that the ban discriminated against transgender troops and harmed military readiness.

"Excluding qualified, fit candidates from service based on sweeping group-based generalizations is irrational," GLAD wrote in a summary of its arguments.

Earlier this month, a federal appeals court in Washington lifted one of the injunctions blocking the ban. The court's decision did not have any immediate effect, however, because the other injunctions remained in place.

President Barack Obama established the policy permitting transgender troops to serve openly in the military in 2016. The Obama administration relied at the time on a study conducted by the RAND corporation that found that there was little impact on readiness or unit cohesion on militaries in other countries that permitted transgender troops.

The cases are Trump v. Karnoski, No. 18-676; Trump v. Jane Doe 2, No. 18-677, and Trump v. Stockman, No. 18-678.