Texas Attorney General Ken Paxton announced Thursday that he is opening an investigation into the San Antonio mayor and city council after the city barred Chick-fil-A from the airport due to what it called "anti-LGBT behavior." The City Council voted 6-4 last week to exclude Chick-fil-A from a new retail and restaurant agreement at the San Antonio International Airport.

Seven years after Chick-fil-A CEO Dan Cathy expressed his support for the "biblical definition of the family unit," the restaurant chain is back in the news after left-leaning website ThinkProgress reported that the Chick-fil-A Foundation gave $1.8 million to three groups with a history of anti-LGBTQ discrimination.

Paxton called the move "the opposite of tolerance" and a "discriminatory decision" based on the religious beliefs of the chain's owners.

"The Constitution's protection of religious liberty is somehow even better than Chick-fil-A's chicken," Paxton said in the letter. "Unfortunately, I have serious concerns that both are under assault at the San Antonio airport."

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The letter also called out multiple council members, including Councilman Manny Peláez. Peláez described Chick-fil-A as a "symbol of hate" because it has donated to religious charities that he considered to oppose LGBTQ rights, CBS San Antonio affiliate KENS-TV reports.

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Mayor Ron Nirenberg said he voted against Chick-fil-A because they are closed Sundays, KENS-TV reports.

"We want to make sure these sub-contracts for restaurants at the airport show off the best of San Antonio," Nirenberg told KENS-TV. "Fifteen percent of volume in the airport happens on a Sunday and we want to make sure there's a restaurant there that's open every day."

In a second letter, Paxton said he would be asking Transportation Secretary Elaine Chao to open an investigation into possible violations of federal law and Transportation Department regulations.