In 2016, the ban on transgender people serving openly in the military was lifted. Now, U.S. President Donald Trump, with the Supreme Court’s approval, has reinstated that ban, citing concerns over transgender service members’ effectiveness in combat.

Kristin Beck, a transgender former Navy SEAL, is calling President Trump’s assertion baseless. “The idea transgender effects ‘Lethality and effectiveness’ which is total BULL SHIT,” she tweeted. In a separate tweet, she wrote that “18 other Nations ALLOW #Trans service members… zero issues!” adding, “I was a Navy SEAL for 20 years — I was pretty lethal.”

During her time in uniform, Beck served with SEAL Teams One and Five, eventually being recruited to Naval Special Development Group (DEVGRU), also known as SEAL Team Six. While in DEVGRU, she deployed to the Balkans, Iraq, Afghanistan, and numerous other undisclosed locations around the world. At one point, she was assigned to a Joint Task Force, which conducted very specialized taskings in Afghanistan. Her military awards include the Bronze Star with valor and the Purple Heart. She retired with the rank of senior chief petty officer (E-8).

“Let’s meet face to face and you tell me I’m not worthy. Transgender doesn’t matter. Do your service,” said Beck in an interview with Business Insider in 2017, when President Trump first tried to reimpose the ban.

Writing of her service in her book “Warrior Princess: A U.S. Navy SEAL’s Journey to Coming out Transgender,” she says that, while in uniform, “I gave true brotherhood. I did my best, 150 percent all the time, and I gave strength and honor and my full brotherhood to every military person I ever worked with.”

Former Secretary of Defense James Mattis agreed with President Trump’s assessment of transgender service members. In a comprehensive review, the Department of Defense (DoD) has concluded that “there are substantial risks associated with allowing the accession and retention of individuals with a history or diagnosis of gender dysphoria and require, or have already undertaken, a course of treatment to change their gender.”

On April 2018, however, the four chiefs of the military branches said in Congress that they found no issue with transgender people serving in the military. “In the last two weeks Gen. Milley [Army Chief of Staff], Gen. Neller [United States Marine Corps Commandant], and Adm. Richardson [Chief of Naval Operations] have told me that they have seen zero reports of issues of cohesion, discipline, or morale as a result of open transgender service in their respective service branches,” said Air Force Chief of Staff General Dave Goldfein Gillibrand.

Despite Beck’s assertions, it is important to note that she served as a man, and not as a transgender service member.