CHICAGO (AP) — Companies cannot discriminate against LGBT employees in the workplace because of their sexual orientation, a federal appeals court said, in a ruling that a gay rights group called a "game changer."

The 8-to-3 decision Tuesday by the full 7th U.S. Circuit Court of Appeals in Chicago is likely to lead to a battle before the Supreme Court over the interpretation of the 1964 Civil Rights Act. This is because a three-judge panel in Atlanta ruled the opposite three weeks ago.

"This decision is a game changer for lesbian and gay employees facing discrimination in the workplace and sends a clear message to employers: it is against the law to discriminate on the basis of sexual orientation," said Greg Nevins, of Lambda Legal, which advocates for LGBT issues.

The case stems from a lawsuit by Indiana teacher Kimberly Hively alleging that the Ivy Tech Community College in South Bend didn't hire her full time because she is a lesbian.

In an opinion concurring with the majority, Judge Richard Posner wrote that evolving norms call for a change in interpretation of the Civil Rights Act, which bars discrimination based on race, color, religion, national origin or sex.

"I don't see why firing a lesbian because she is in the subset of women who are lesbian should be thought any less a form of sex discrimination than firing a woman because she's a woman," wrote the judge, who was appointed by Republican Ronald Reagan.

The decision comes as President Donald Trump's administration has begun setting its own policies on LGBT rights. Late in January, the White House declared Trump would enforce an Obama administration order barring companies that do federal work from workplace discrimination on the basis of sexual identity. But in February, it revoked guidance on transgender students' use of public school bathrooms, deferring to states.

Hively said after Tuesday's ruling that she agreed to bring the case because she felt she was being "bullied." She told The Associated Press in a telephone interview that the time has come "to stop punishing people for being gay, being lesbian, being transgender."

Ivy Tech said in a statement that its policies specifically bar discrimination based on sexual orientation and that it denies discriminating against Hively, a factual question separate from the 7th Circuit's finding regarding the law.

The Chicago ruling came on the anniversary of the assassination of civil rights icon Martin Luther King, whose marches against racism prompted Congress to pass the landmark civil rights law. A GOP-majority House and Senate make it unlikely the current Congress will amend the law.

Debate in the Hively case revolved around the meaning of the word 'sex' in Title VII, the section of the law that deals with discrimination. Other courts have concluded that Congress meant for the word to refer only to whether a worker was male or female. They said that it would be wrong to stretch the meaning of 'sex' in the statute to include sexual orientation.

The majority of the 7th Circuit sided with a broader meaning.

"Any discomfort, disapproval, or job decision based on the fact that the complainant — woman or man — dresses differently, speaks differently, or dates or marries a same-sex partner, is a reaction purely and simply based on sex. That means that it falls within Title VII's prohibition against sex discrimination," Judge Diane Wood, a President Bill Clinton appointee, wrote for the majority.

The dissenting opinion — written by Judge Diane Sykes, a conservative who was on Trump's list of possible Supreme Court appointees — said the majority were stretching the meaning of the law too far.

"We are not authorized to infuse the text with a new or unconventional meaning or to update it to respond to changed social, economic, or political conditions."

The dissent alludes to the judicial philosophy of Trump's high-court nominee, Neil Gorsuch, who advocates sticking with the original legislative texts in deciding legal disputes.

"It's understandable that the court is impatient to protect lesbians and gay men from workplace discrimination without waiting for Congress to act. Legislative change is arduous and can be slow to come. But we're not authorized to amend Title VII by interpretation," Sykes wrote.

Posner, though, said sticking to original meanings and cultural standards didn't make sense.

"It is well-nigh certain that homosexuality, male or female, did not figure in the minds of the legislators who enacted Title VII," he wrote in his concurring opinion.

"(Lawmakers in the 1960s) shouldn't be blamed for that failure of foresight," he wrote. "We understand the words of Title VII differently not because we're smarter than the statute's framers and ratifiers, but because we live in a different era, a different culture."