As the national furor continues over a controversial religious freedom law in Indiana that critics say could allow businesses to discriminate against LGBT customers, one troubling fact is being left out of the debate: in 29 states, it's already legal for a store owner to deny service to a gay person based on his sexual orientation.

While legal experts doubt Indiana's Religious Freedom Restoration Act (RFRA) could be used to justify discrimination when it takes effect on July 1, most states, including Indiana, have long allowed it to happen because they don't have civil rights laws that would prohibit discrimination against LGBT people in the workplace, housing, and public accommodations (hotels, restaurants, and other places that serve the general public). It's not the religious freedom laws that allow discrimination; it's the lack of civil rights laws.

As a result, in many states an employer can legally fire someone because he's gay, a landlord can legally evict someone because she's lesbian, and a hotel manager can legally deny service to someone who's transgender — without citing religious grounds.

It's not the religious freedom laws that allow discrimination; it's the lack of civil rights laws

Indiana in particular has no statewide nondiscrimination law for LGBT people, although about a dozen cities, including Indianapolis, have local measures.

"That's what's missing in the Indiana debate," Robin Wilson, a law professor at the University of Illinois, said. "If there's a 'license to discriminate,' it's the fact that the state hasn't said this is an unacceptable basis for saying no to people."

But it's not just Indiana. Depending on how you add it up, as many as 33 states don't have full protections for all LGBT people, because a few states with nondiscrimination protections don't protect trans people, and some don't ban all anti-LGBT discrimination in public accommodations.

Currently, 19 states ban discrimination based on sexual orientation and gender identity, while three additional states ban discrimination based on sexual orientation. Some other states protect public but not private employees from discrimination. Many municipalities have nondiscrimination laws that only apply within their local borders. And some companies prohibit discrimination in their own policies.

The protections sometimes vary from state to state. Massachusetts's protections for gender identity and Utah's protections for sexual orientation and gender identity don't apply to public accommodations. Some states, like Utah, also include exemptions for discrimination based on religious grounds.

LGBT advocates argue the Civil Rights Act of 1964 already protects LGBT workers from discrimination, but that interpretation of the federal law hasn't been proven in court.

Watch: How most states still discriminate against LGBT people

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