Olympic champion Caster Semenya is challenging a recently introduced IAAF regulation, calling it "discriminatory."

The two-time Olympic gold medallist in the 800 metres filed a legal case on Monday before the Court of Arbitration for Sport in Lausanne, Switzerland, challenging the IAAF's recently introduced Eligibility Regulations for Female Classification.

"I am very upset that I have been pushed into the public spotlight again. I don't like talking about this new rule," the South African athlete said in a release. "I just want to run naturally, the way I was born."

"It is not fair that I am told I must change. It is not fair that people question who I am."

According to Semenya and her legal team, the IAAF regulation requires women who compete in athletics at the international level to submit to medically unnecessary interventions to lower their natural testosterone levels.

"Ms. Semenya contends that the regulations are objectionable on numerous grounds, including that they compel women with no prior health complaints to undergo medical interventions to lower their testosterone levels in the absence of support by the available science," said her legal team, which includes lawyers in South Africa and Toronto's James Bunting, who has had previous success at the CAS challenging the IAAF's testosterone rules.

Her team also contends the new regulation "continues the offensive practice of intrusive surveillance and judging of women's bodies which has historically haunted women's sports."

"The regulations stigmatize and cause harm to women, and legitimize discrimination against women in sport who are perceived as not adhering to normative ideas about femininity."

Unfair advantage? Some opponents think so

Though she has identified as a woman her entire life, the 27-year-old is also considered intersex, meaning she was born with a reproductive or sexual anatomy that does not conform to traditional definitions of male or female. Semenya has a medical condition known as hyperandrogenism, characterized by elevated levels of male sex hormones — such as testosterone — in the female body.

Since testosterone is one of the key ingredients contributing to an athlete's strength and speed, many — including some of her competitors — feel Semenya has an unfair advantage.

After Semenya won both the 800 and 1,500 in convincing fashion at April's Commonwealth Games, Australian runner Brittany McGowan suggested it wasn't possible to keep up with her.

"It's tough for a lot of women in the 800, 400 and 1,500 at the moment to compare ourselves and be judged by our governing bodies on those times," McGowan said.

South Africa's Caster Semenya set a new women's 800m meet record, at the IAAF Diamond League's Prefontaine Classic in Eugene Oregon, with a time of 1:55.92 5:47

At the 2016 Rio Olympics, Poland's Joanna Jozwik was even more pointed after finishing fifth in the 800 final. Francine Niyonsaba of Burundi and Kenya's Margaret Wambui, who finished second and third in the race, respectively, have also faced questions about their powerful-looking physiques.

"It is a little strange that the authorities do nothing about this," Jozwik said. "These colleagues have a very high testosterone level, similar to a male's, which is why they look how they look and run like they run."

Latest chapter in lengthy saga

Semenya and her elevated testosterone levels have long been the focus of the IAAF. In July 2015, the CAS ruled the IAAF's initial testosterone-limiting move was discriminatory and suspended it.

The IAAF, though, was given time to shore up its case and bring it back to the court. It was told to prove that athletes like Semenya with elevated testosterone levels have an advantage in the range of 10-12 per cent over other women.

It took nearly three years, but the IAAF responded last month with a new set of regulations for what it calls Athletes with Differences of Sexual Development (DSD) — backed by a study that was quickly called into question.

Semenya won the women's 800m race at the opening Diamond League event in Doha. Under a new and controversial rule, Semenya will be forced to suppress her hormone levels in order to compete, beginning November 1. 7:27

Under the new rules, which are set to take effect Nov. 1, in order to be allowed to compete in women's track events between 400 and 1,500 metres, so-called DSD athletes must be recognized by law as either female or intersex and must maintain testosterone levels of five nanomoles per litre of blood or less.

"We want athletes to be incentivized to make the huge commitment and sacrifice required to excel in the sport, and to inspire new generations to join the sport and aspire to the same excellence," IAAF president Sebastian Coe said.

'Arbitrary' rule called into question

Since Coe and the IAAF introduced the new rules, many have questioned the intent.

"The IAAF has a duty to show that there is a reasonable scientific basis for this rule," said lawyer Paul Greene, who has argued numerous cases to the CAS.

"To me, this rule is even more arbitrary in that it includes some events and not other events. It doesn't make any sense to me. How could testosterone help a woman in the 400 or 800 but not in the 100 or 200?"

"They were arguing just two years ago that a 100-metre runner couldn't compete because her testosterone level was too high. Now, two years later, they are saying a 100-metre runner can compete. Maybe their science backs that up. Maybe they have new science and different studies. But I know just a few years ago, when they made similar arguments, they were rejected," Greene said.

Semenya's lawyers said this challenge is being filed "to ensure, safeguard and protect the rights of all women," calling the new regulations "discriminatory, irrational, unjustifiable, and in violation of the IAAF Constitution and the Olympic Charter."

The timing of this is key. The new IAAF regulation comes into effect in November and women must show lowered testosterone levels for a minimum of six months before they can be considered eligible to compete. Semenya is asking the IAAF to suspend the implementation of the rule until her legal challenge is decided.

"I am Mokgadi Caster Semenya. I am a woman and I am fast," says Semenya.