WASHINGTON — The Equal Employment Opportunity Commission has ruled that existing civil rights law bars sexual orientation-based employment discrimination — a groundbreaking decision to advance legal protections for gay, lesbian, and bisexual workers.

"[A]llegations of discrimination on the basis of sexual orientation necessarily state a claim of discrimination on the basis of sex," the commission concluded in a decision dated July 15.

The independent commission addressed the question of whether the ban on sex discrimination in Title VII of the Civil Rights Act of 1964 bars anti-LGB discrimination in a complaint brought by a Florida-based air traffic control specialist against Transportation Sec. Anthony Foxx.

The ruling — approved by a 3-2 vote of the five-person commission — applies to federal employees' claims directly, but it also applies to the entire EEOC, which includes its offices across the nation that take and investigate claims of discrimination in private employment.

While only the Supreme Court could issue a definitive ruling on the interpretation, EEOC decisions are given significant deference by federal courts.

In 2012, the commission addressed a similar issue regarding whether transgender workers are protected under the sex discrimination ban from discrimination. There, in a case brought by Mia Macy against the Bureau of Alcohol, Tobacco, Firearms and Explosives, the commission ruled that gender identity-based discrimination is barred by the sex discrimination ban. In December 2014, the Justice Department announced a similar view of the law — stating that it would apply that interpretation in its cases.

While the EEOC had been pushing toward today's decision with cases and even field guidance addressing coverage under Title VII of specific types of discrimination faced by gay people, the July 15 decision states that "sexual orientation is inherently a 'sex-based consideration.'"

In reviewing courts' prior interpretation of the words of Title VII, the commission acknowledged plainly that sexual orientation itself is not listed as a type of discrimination barred in the 1964 law.

"[T]he question is not whether sexual orientation is explicitly listed in Title VII as a prohibited basis for employment actions. It is not," the commission found. Instead, the commission stated that the question is the same as in any other Title VII sex discrimination case: "whether the agency has 'relied on sex-based considerations' or 'take[n] gender into account' when taking the challenged employment action."

The commission found that sexual orientation discrimination is sex discrimination for several reasons. Among the reasons, the commission stated, is because sexual orientation discrimination "necessarily entails treating an employee less favorably because of the employee's sex" and "because it is associational discrimination on the basis of sex."

After a review of the case law regarding similar challenges to employment practices alleging a violation of Title VII where the initial understanding of the law would not have included that coverage, the commission stated, "The courts have gone where the principles of Title VII have directed."

"Our task is the same," the decision found. "We therefore conclude that Complainant's allegations of discrimination on the basis of sexual orientation state a claim of discrimination on the basis of sex. We further conclude that allegations of discrimination on the basis of sexual orientation necessarily state a claim of discrimination on the basis of sex."

Tico Almeida, the head of Freedom to Work, celebrated the decision — and urged LGBT groups to go to the courts to seek codification of the ruling.

"Freedom to Work applauds this historic decision by the EEOC, and we encourage gay men, lesbians, and bisexuals who face harassment or discrimination on the job to consult an attorney and file Title VII claims with the EEOC and eventually the federal courts," he said. "Our LGBT movement should take this strongly reasoned legal victory and run with it by returning to the federal courts to win workplace protections in all fifty states.

The Human Rights Campaign's president, Chad Griffin, pushed for legislative action to confirm the protections.

"This historic ruling by the EEOC makes clear they agree workplace discrimination on the basis of sexual orientation, much like gender identity, is illegal," he said, adding, "While an important step, it also highlights the need for a comprehensive federal law permanently and clearly banning LGBT discrimination beyond employment to all areas of American life. Such a law would send a clear and permanent signal that discrimination against LGBT people will not be tolerated under any circumstances in this country, and we remain fully committed to making that happen."

Almeida, however, shot back, "I bet we can get LGBT workplace or housing cases to the U.S. Supreme Court sooner than the U.S. House of Representatives will allow an up-or-down vote on a comprehensive LGBT non-discrimination bill."