The Fairness In Women's Sports Act is a common title for legislation passed in Idaho, Florida, and Arkansas that restricts participation in interscholastic, intercollegiate, intramural, club athletic teams, and any sports sponsored by a public school or university based on the assigned sex of the individual. The legislation was introduced in response to concerns that allowing transgender women to compete in women's sports would create an unfair advantage due to their physiological differences. This bill generally prohibits school athletic programs from allowing individuals whose assigned sex at birth was male to participate in programs that are for women or girls. (R-AL)
Legislation of this nature has been introduced in several states across the US and is part of a national debate over whether transgender athletes should be allowed to compete in sports teams based on their gender identity. In January 2025, the United States House of Representatives passed similar legislation titled "Protection of Women and Girls in Sports Act" that restricts transgender women from playing on women's sports teams.
Supporters of the laws argue that it is necessary to maintain fair competition and protect the integrity of women's sports, while opponents argue that they are discriminatory and unjust. Such legislation has faced legal challenge but, on June 30, 2026, the Supreme Court of the United States upheld Idaho's "Fairness in Women's Sports Act" along with similar legislation in other states in the court case Little v. Hecox.
Background Research shows that men have increased muscle mass and strength, different skeletal structures, and better-adapted cardiorespiratory systems that put them at an advantage during sports over women, and that male physiology cannot be reformatted by estrogen therapy in transwoman athletes because testosterone has driven permanent effects through early life exposure. Due to these biological differences, there have been debates about whether transgender athletes, specifically transgender women, should be allowed to participate with cisgender athletes, specifically cisgender women. Opponents to the participation of transgender women in women's sport believe that transgender women have an unfair advantage over cisgender women due to the differences in human physiology and that these differences are not reversed enough with hormone therapies, while supporters believe that hormone therapies and puberty blockers reduce the competitive advantages.
The first transgender athlete who was banned from competing was Renee Richards. Renee Richards was an American tennis player who was banned from competing in the US Open in 1976. The following year Renee won the right to compete in the New York Supreme Court in 1977.
In 2003 the International Olympic Committee issued its first set of guidelines regarding transgender participation in sports. It required that transgender athletes undergo gender reassignment surgery followed by at least two years of hormone therapy in order to be eligible for competition. In 2016, the IOC revised its guidelines to remove the requirement for surgery and all restrictions on female-to-male transgender athletes. Male-to-female transgender athletes were required to prove their testosterone levels below 10 nanomols per liter for at least a year prior to competing. In November 2021, the IOC removed the testosterone cut off. Instead, it recommended each sport design their own rules, including banning transgender competitors if necessary.
In March 2026, the IOC issued a new policy banning transgender women from competing in women's events. The IOC said women's events would be restricted to "biological females" whose sex would be determined by a mandatory gene test.
Scientific basis Alison Heather, a professor of physiology at the University of Otago in New Zealand studied the physiological differences between biological females and biological males and how gender-affirming hormone therapy affects those differences. She asserts there are immutable differences between the sexes in the brain, skeletal structure, and cardiorespiratory system and differences in muscle mass, strength, and aerobic capacity which can be modified through hormone therapy. Heather attributes these cardiorespiratory differences to the levels of testosterone exposure in the first years of life. While accounting for sex variation, cisgender women have a 10-12% smaller lung capacity than cisgender men and a shorter diaphragm. Similarly, a cis woman's heart is 85% the size of a cis man's heart. Additionally, Heather found biological males have an advantage in spatial ability, visual memory tasks, and perception. When compared with trans women after a year of estrogen therapy, there was no decrease in these cognitive advantages. Prolonged estrogen therapy can diminish some of these advantages. Heather also found that estrogen therapy cannot alter skeletal structure, but it does diminish muscle mass.
The British Journal of Sports Medicine published research by Dr. Timothy Roberts, Joshua Smalley, and Dale Ahrendt, MD. which examined the effects of gender-affirming hormone therapy on the athletic performance of trans men and trans women in the U.S. Air Force. They found prior to hormone therapy transgender women performed 31% more push ups, ran 1.5 miles 12% faster than cisgender women, and performed 15% more sit-ups. After two years of hormone therapy, trans women had no advantage in push-ups or sit-ups but maintained a 12% advantage in running. Additionally, prior to hormone therapy, transgender men accomplished 43% fewer push-ups than cis men and ran the 1.5 miles approximately 15% slower. After one year of hormone therapy, there was no difference between cis men and trans men in push-ups or run times, but trans men accomplished more sit-ups on average than cisgender men.
Legislation Idaho On March 30, 2020, the Governor of Idaho signed into Law House Bill No. 500 entitled "Fairness in Women's Sports Act." The bill amended Title 33 of the Idaho Code with the addition of a new chapter 62 to be known and cited as the "Fairness in Women's Sports Act." This bill established that only female students who were biologically female at birth can participate in female sports teams and athletics. It states that public schools, any school that is a member of the Idaho High School Activities Association, and any higher education institution that is a member of the NCAA, NAIA, or NJCAA must ensure that athletic teams are designated based on biological sex, rather than gender identity, and prohibits transgender females from participating in female sports teams. The bill made Idaho the first state to outright ban transgender participation in athletics.
The bill was introduced in response to growing concerns that allowing transgender females to compete in women's sports would create an unfair advantage due to their physiological differences. Males, as the bill outlines, having naturally higher levels of testosterone, higher red blood cell counts, high hemoglobin, larger hearts, greater lung volume per body mass, and other biologically advantageous traits, are able to generate greater power and speed during physical activity than their female counterparts. Citing Neil Burton's article "The Battle of the Sexes" published in 2012, Gina Kolata's article "Men, Women, and Speed. 2 Words: Got Testosterone?" published in 2008, and the work of Doriance Lambelet Coleman among others, the bill provides extensive scientific evidence to support its claim of an inherent male advantage over females in athletic pursuits.
The legal footing of the bill is found in the U.S. Supreme court ruling in United States v. Virginia (1996) which stated that "sex classifications may be used to compensate women for particular economic disabilities suffered, promote equal employment opportunity, [and] to advance full development of the talent and capacity of our Nation's people." Emphasizing the final clause, the Idaho legislature argues that sex classifications are necessary for the "full development of the talent and capacity of our Nation's people" in the context of sports and athletics. The bill also cites two cases, Kleczek v. Rhode Island Interscholastic League, Inc. and Petrie v. Illinois High School Association, wherein the courts have recognized the existence of inherent physiological differences between males and females and the unfair advantage those differences give males over females in athletics. Thus, it is only through teams and sports designated based on biological sex that the state of Idaho could fully realize gender equality in sports and athletics.
House Bill No. 500 specifies that a "student may establish sex by presenting a signed physician's statement that shall indicate the student's sex based solely on: the student's internal and external reproductive anatomy; the student's normal endogenously produced levels of testosterone; and an analysis of the student's genetic makeup." The bill makes clear that even those using puberty blockers and cross-sex hormones if born biologically males continue to have an absolute advantage over female athletes and should be excluded from female-designated athletics.
Supporters of the bill argue that it is necessary to protect the integrity of women's sports and ensure a level playing field for female athletes. Opponents of the bill argue that it is discriminatory against transgender individuals and violates their rights to equal treatment under the law as guaranteed in the Equal Protection Clause of the U.S. Constitution.
Florida Florida Governor Ron DeSantis signed the "Fairness In Women's Sports Act" into law on July 1, 2021. This legislation is intended to maintain fairness and opportunities for female student-athletes. Similar to the Idaho bill, the Florida Act relies on biological sex at the time of birth as declared on the student's birth certificate but does not require anatomy to be certified by a physician. The bill requires all post-primary public institutions to designate sex-specific sports and teams. The bill designates three categories of teams and sports. The first is male-sex only but may allow athletes of the female sex. The second is female-sex only and this category cannot allow students of the male sex. The third category is co-ed and accepts students of both male and female sex.
Unlike the Idaho bill, the Florida legislation does not discuss biological differences between the male and female sex, and private schools are largely exempt from the sex-designation requirement. This bill is also designed to protect public educational institutions from investigations, lawsuits, or complaints on the basis of female-only sports and teams. It allows for any students or organizations who are harmed by institutions that do not maintain female-only teams to take action for injunctive relief to file private claims within two years of the harm occurring. Harm can be defined as the deprivation of athletic opportunity, or subjection to public, athletic, or educational retaliation for reporting violations of the law. If their claims are determined to be factual they can be rewarded monetary restitution for harms that may include, physical, emotional, and psychological damage as well as attorney fees and are eligible for "any other appropriate relief" as the civil courts see fit.
Arkansas Arkansas Senate Bill 354 To Create The Fairness in Women's Sports Act was signed into law by the Governor on March 29, 2021. SB354, which draws heavily from the Idaho House Bill No. 500, amends the Arkansas Code Title 6, Chapter 1, Subchapter 1 to create a section entitled "Fairness in Women's Sports Act." The bill, like that of Idaho's, established that only female students may participate in female sports teams and athletics, and banned the participation of transgender students in any sport or athletic pursuit designated as female.