“I just want to play football. … It’s a part of me,” she said. “It will always be a part of me. It’s half of what made me who I am.”

Tirrell and her parents have not given up hope. They, along with another transgender teenager and her parents, are suing New Hampshire to prevent the law from being enforced. Their lawyers, from three law firms that support LGBTQ+ rights, filed a lawsuit in federal court Friday morning, urging a judge to quickly intervene.

Chris Erchull, a senior attorney at GLBTQ Legal Advocates & Defenders (GLAD), said Tirrell’s lawyers knew their first football game of the season was scheduled for Aug. 30 and therefore expected to have to file a lawsuit before that event.

“But now it is obvious that we need help even more urgently,” Erchull said, noting that the plaintiffs are asking the court for an injunction.

Otherwise, the immediate harms resulting from the implementation of this new law will be felt as early as next week and will have a deeply personal and stigmatizing impact on Tirrell, he said.

“This is the perfect example of why this law is so unfair and cruel,” he added. “She won’t be able to go to soccer practice with her friends on Monday, and they will know why – and if they don’t know, they will ask why.”

Although supporters of House Bill 1205 said the law would ensure fairness and safety for girls in athletic competition, Erchull said it is clearly aimed at targeting transgender girls, who now face unfair treatment that undermines their safety. The lawsuit alleges that enforcement of the new law violates Title IX and the 14th Amendment’s equal protection principle.

“It is cruel and unnecessary and serves no interest that the state could actually justify,” Erchull said.

A spokesman for Gov. Chris Sununu referred questions about the lawsuit to the New Hampshire Department of Justice. A Department of Justice spokesman said the state’s attorneys are reviewing the complaint “and will respond accordingly.”

Sununu, a Republican, signed HB 1205 on July 19, with the new law set to take effect 30 days later. He said it would “ensure fairness and safety in women’s sports by maintaining integrity and competitive equity in athletic competitions,” with a political stance that has now become mainstream.

“With this widely supported move, New Hampshire joins nearly half of all U.S. states that have taken this action,” he said.

While about half of all states have passed such bans in the wake of a wave of anti-LGBTQ+ laws, New Hampshire is the first state in the Northeast to do so.

The lawsuit says being transgender is “not a reliable indicator of athletic performance or ability.” Tirrell has been taking puberty-blocking medication since May 2023, so she has not and will not experience the physiological changes and increased testosterone levels of male puberty, the lawsuit says. Instead, the hormones she took caused her to experience physiological changes associated with puberty in girls.

The lawsuit goes on to say that sport was an important source of social contact for Tirrell and that switching to a boys’ team was not a sensible option for her.

“Parker is a girl. It would be painful and humiliating to be forced to play on a boys’ team,” the lawsuit states. “It would also undermine her treatment for gender dysphoria.”

Tirrell said she had hoped to one day win an athletic scholarship, but the idea that she had an unfair advantage or posed a physical threat to her teammates was not realistic: She is 5-foot-6 and has less muscle mass than some of her peers – not exactly the imposing figure that policymakers seem to have in mind.

“They imagine a trans girl as a big, muscular, buff bodybuilder. I feel like that’s how they imagine it,” she said, attributing the right’s obsession with measures like this to a general sense of nervousness about increasing societal acceptance of trans and nonbinary people. “I think they’re scared.”

Under the new restrictions in HB 1205, public schools that educate students in fifth through 12th grade and private schools whose students compete against public schools must declare their school sports and club athletics teams as either men’s or women’s teams, or as teams from both groups.

The law prohibits biological males from participating on all-female teams. A student’s gender is determined by their unaltered birth certificate. If a birth certificate “does not appear to be original” or gender at birth is not indicated, the student must “provide other proof indicating the student’s gender at the time of birth” and pay all associated costs.

Critics warned that the lack of clarity about what “further evidence” students must provide when their gender is questioned could lead to problems.

The law requires the State Board of Education, all local school boards, and the governing boards of all public charter schools in New Hampshire to adopt and enforce compliance policies. It also provides students with the ability to sue schools for alleged noncompliance with the new rules.

In an email to Tirrell’s parents on Thursday, Kyla A. Welch, superintendent of the Pemi-Baker Regional School District, wrote that the district must begin enforcing the restrictions “even though it has not yet issued policies to ensure compliance with the new law.” The law prohibits Tirrell from participating on the football team, and only members of the football team are allowed to practice with the team, she wrote.

The other plaintiff in the suit is Iris Turmelle, 14, a rising ninth-grader at Pembroke Academy. She has tried tennis and shown interest in javelin throwing, but said she is “definitely not” an elite athlete. For her, the sport is primarily a way to gain social, academic, physical and emotional advantages, the suit says.

“It’s unfair to single out girls like me and Parker for no good reason,” she told the Globe.

Turmelle’s mother, Amy Manzelli, said she hopes Granite State residents can empathize with her, her husband and her daughter, who are being denied part of their high school experience.

“We are a normal family … and we just want our wonderful daughter – our wonderful daughter who is not an elite athlete – to have the right to play sports for the same reasons that other girls and boys want to play sports,” Manzelli said.

The two families are represented by attorneys Erchull and Ben Klein at GLAD, Henry Klementowicz and Gilles Bissonnette at the American Civil Liberties Union of New Hampshire, and Louis Lobel, Kevin DeJong and Elaine Blais at Goodwin.

The defendants are New Hampshire State Commissioner of Education Frank Edelblut, each of the seven members of the State Board of Education, Pemi-Baker Regional School District and each member of its board, and Pembroke School District and each member of its board.

This report has been updated with a statement from the Justice Department. Globe writer Amanda Gokee contributed to this report.

Steven Porter can be reached at [email protected]. Follow him @Reporterporter.