The other two complainants, who also run track, have chosen to remain anonymous.
"Girls deserve to compete on a level playing field. Forcing female athletes to compete against boys is grossly unfair and destroys their athletic opportunities," said ADF Legal Counsel Christiana Holcomb in a statement posted on the organization's website.
"Title IX was designed to eliminate discrimination against women in education and athletics, and women fought long and hard to earn the equal athletic opportunities that Title IX provides. Allowing boys to compete in girls' sports reverses nearly 50 years of advances for women under this law."
Speaking on Fox News, Soule said that she has received "nothing but support" from her teammates and from other athletes, but she has "experienced some retaliation from school officials and coaches."
In a 2018 interview after the state championships, Soule said that she had "no problem with [the male athletes] wanting to be a girl," but that she did not think it was right that she had to race males.
"I think it's unfair to the girls who work really hard to do well and qualify for Opens and New Englands," she said in 2018. The New England championships serve as a scouting venue for many college-level coaches.
Earlier this month, the Congregation for Catholic Education issued a document laying out principles for Catholic engagement with so-called gender theory, which posits that biological sex and gender are intrinsically mutable and seperable.
The document, titled "Male and Female He Created Them," called gender theory an effort "chiefly to create a cultural and ideological revolution driven by relativism, and secondarily a juridical revolution, since such beliefs claim specific rights for the individual and across society."
"There is a need to reaffirm the metaphysical roots of sexual difference, as an anthropological refutation of attempts to negate the male-female duality of human nature, from which the family is generated," said the document.
"The denial of this duality not only erases the vision of human beings as the fruit of an act of creation but creates the idea of the human person as a sort of abstraction who 'chooses for himself what his nature is to be.'"