The US Department of Justice filed a lawsuit against Southeastern Oklahoma State University for alleged discrimination against a transgender professor, BuzzFeed's Chris Geidner reported. The Justice Department claims the university denied a promotion and tenure application to Rachel Tudor because she identifies with a gender different from the one she was assigned at birth. The Justice Department cited the Civil Rights Act of 1964 in its challenge, making this the first time the federal government has touted the civil rights law in defense of trans people in a lawsuit. The claim argues the Civil Rights Act's workplace sex discrimination ban prohibits discrimination based on gender identity.

How the Civil Rights Act could protect LGBT rights

More than 50 years after Congress passed the landmark civil rights legislation, advocates hope the law can be used to protect LGBT workers.

The Civil Rights Act prohibits various forms of discrimination on the basis of race, color, religion, sex, or national origin, in part allowing those who have been discriminated against in the workplace to take legal action against their employers. The question for LGBT advocates is whether Title VII of the Civil Rights Act, which in part prohibits workplace discrimination on the basis of sex, also applies to gay, lesbian, bisexual, transgender, and gender-nonconforming workers.

THE QUESTION IS WHETHER PROTECTIONS ON THE BASIS OF SEX ALSO APPLY TO LGBT WORKERS

The US Supreme Court in 1989 decided that Title VII protects workers from sex stereotyping, such as assuming a woman must present herself in a feminine manner. Advocates argue those protections can extend to any social stereotype or expectation based on sex that LGBT people might defy in the workplace.

"It's pretty uncontroversial that discriminating against a man who acts too effeminate or a woman who acts too masculine is a form of sex discrimination," ACLU LGBT and AIDS Project staff attorney Josh Block told me last year. "That applies to lesbians and gay men, too."

The US Equal Employment Opportunity Commission (EEOC) agrees with LGBT advocates. In multiple rulings in 2011 and 2012, EEOC concluded that Title VII's protections against sex discrimination protect transgender and gender-nonconforming workers and, in some cases, gay, lesbian, and bisexual people. The Justice Department has agreed to respect those decisions.

But there's one catch: EEOC rulings aren't the law of the land. Courts facing workplace discrimination cases typically consider the EEOC rulings as expert advisories and nothing more, potentially leaving private workers in the dark.

The EEOC and Supreme Court, for example, once disagreed on whether federal law indefinitely prohibits discriminatory pay practices against women. It took Congress's approval of the Lilly Ledbetter Fair Pay Act to establish stronger pay protections for women.

Along the same lines, it could take congressional action or a Supreme Court decision to ensure all US courts follow the EEOC's interpretation.

"We think the EEOC's position is absolutely the correct legal position, and it should be very persuasive to any court, including the Supreme Court," Block said. "But when you're talking about basic human rights … you want explicit protections in the law."

Read the Justice Department's full lawsuit.

Watch: How most states still discriminate against LGBT people

Further reading