When the girls' soccer team at Plymouth Regional High School in New Hampshire began practice on Monday to prepare for the start of the official season on Aug. 30, transgender athlete Parker Tirrell was able to join her teammates.

That's what a federal judge ruled on Monday after the families of two transgender teens -- 15-year-old Tirrell and 14-year-old Iris Turmelle -- filed a lawsuit Friday, days before a new law went into effect that would have prohibited them from playing with teams that align with their gender identity.

They argued that the legislation is in violation of the teens' Title IX rights, the civil rights law that prohibits sex-based discrimination in educational settings that receive federal funding.

"Sports has been a source of joy for her and has been the primary way she makes friends and experiences a sense of belonging and connection to others. Soccer is her real passion," the suit said of Tirrell. "She played on the girls' soccer team last year in ninth grade and is excited to rejoin her team when the season officially starts again."

The suit came after Tirrell's school reached out to the teen's mother last Thursday, informing her that she would not be allowed to participate in soccer practice. Initial phases of the law, signed last month by Republican Gov. Chris Sununu, were set to go into effect on Monday – the same day soccer practice was scheduled to start.

The new law requires schools to designate teams as boys, girls or coed. Eligibility for athletes under the law is determined based on the sex assigned on birth certificates, or "other evidence." Gov. Sununu said in a statement following the signing. He said the bill "ensures fairness and safety in women's sports by maintaining integrity and competitive balance in athletic competitions."

Sununu's office did not immediately respond to ABC News' request for comment.

Chief Judge Landya B. McCafferty ruled in favor of the plaintiffs on Monday as it related to Tirrell's case. In her ruling, she said the state and school district "must permit plaintiff Parker Tirrell to try out for, practice with, compete with, and play on the school sports teams designated for girls on the same terms and conditions as other girls."

"Parker's on her way to soccer practice now," Chris Erchull, Senior Staff Attorney at GLBTQ Legal Advocates & Defenders (GLAD) and attorney representing Tirrell and Turmelle, told ABC News following the ruling. "And she is authorized to play."

Legal representatives for the New Hampshire Department of Education Commissioner, the New Hampshire State Board of Education, the Pemi-Baker Regional School District and the Pemi-Baker Regional School Board Members did not immediately respond to ABC News' request for comment.

Monday's ruling only applies to Tirrell's case -- the lawyers filed an emergency order ahead of the first day of soccer practice, which coincided with the day the law was set to be enacted.

Turmelle, who is entering the ninth grade, played intramural tennis in middle school and plans to try out for the girls' tennis and track teams (which are winter and spring sports) upon entering high school, according to the complaint. It notes that she hopes participation in sports will help her make more friends, establish a peer group and cope with the stresses she experiences in life.

Judge McCafferty's order will remain in effect until the next hearing on Aug. 27, unless an extension is issued by the judge. Both Tirrell and Turmelle's cases will be heard then, marking the first time Turmelle's case comes before the judge.

"It's what we expected the outcome to be because we knew we were right on the law, and we knew we were right about the rights of our plaintiffs," Erchull said.