Saying the federal government "has a significant interest in the proper interpretation of Title IX," the U.S. Department of Justice filed a statement of interest in a case that could decide whether transgender athletes can compete in girl's high school sports in Connecticut.

In its 13-page brief, the Justice Department on Tuesday took aim at the Connecticut Interscholastic Athletic Conference, the primary defendant in a lawsuit in which three high school girls claim they are at a disadvantage in competing with transgender athletes in sports such as track and field.

The athletic conference, the Justice Department wrote, "has adopted a policy that requires biological males to compete against biological females, despite the real physiological differences between the sexes if the male is a transgender individual who publicly identifies with the female gender."

At issue in Connecticut was a lawsuit that a conservative nonprofit filed last month on behalf of the three high school students. That group, the Alliance Defending Freedom, claimed  transgender athletes have an unfair athletic advantage. The group, according to its website, is pro-life, supports heterosexual marriage and advocates for religious freedom.

The Justice Department's brief further says that Title IX "and its implementing regulations prohibit discrimination solely 'on the basis of sex' and not on the basis of transgender status." The brief also states that Title IX "consistently uses 'sex' as a binary concept capturing only two categories: male and female."

While the Justice Department has written amicus briefs for issues related to Title VII of the Civil Rights Act, which encompasses labor law, the statement of interest filed Tuesday in Connecticut federal court appears to be the first time the U.S. government has weighed in on a Title IX legal issue related to transgender athletes in high school.

The Justice Department submitted a brief last year asking the U.S. Supreme Court to conclude that Title VII doesn't protect transgender people from employer discrimination.

According to a Connecticut expert in Title IX laws, Main Justice's filing doesn't coincide with the facts.

Nina Pirrotti, a partner with New Haven-based Garrison, Levin-Epstein, Fitzgerald & Pirrotti, said the Trump administration often gets involved in litigation across the country siding against the interest of the LGBTQ community.

"The broader issue is that they are using Title IX as a sword, rather than a shield. It's about trying to marginalize one of the most vulnerable segments of our population, which are transgender people," Pirrotti said,

Pirrotti continued: "Everything the Trump administration has done with respect to Title IX is consistent with this approach. It's chipping away at Title IX protections and that includes transgender people. This narrows the class of people who can seek protection under Title IX."

Pirrotti noted the statement of interest "specifically references the potential consequences if these [transgender] girls can participate, which, the government says, includes paving the way toward transgender people being allowed to use the bathroom pertaining to the sex for which they identify."

The Trump administration in 2016 rescinded DOJ guidance issued under President Barack Obama that said federally funded schools should allow transgender children to use the bathroom of their choice.

Leading the fight for the three female students is Christiana Holcomb, legal counsel for the nonprofit that filed the lawsuit. Holcomb couldn't be reached for comment Wednesday, but in February she said, "What we are seeing in Connecticut is that when you allow biological males to play in the girls' categories across the board, girls lose that level playing field and the benefits and opportunities that Title IX was designed to provide."

The Justice Department's brief was signed by Matthew Donnelly, an attorney in the Civil Rights Division.

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