In the build-up to the 2009 world championships in Berlin, where Semenya went on to win gold in the 800m, the South African had to undergo gender verification testing.
The South African double Olympic 80m champion is locked in a bitter dispute with the IAAF.
Semenya was free to run after Switzerland's top court on Wednesday rejected an IAAF request to re-impose rules obliging her to lower her testosterone before competing in certain events.
The athlete was contesting a decision by the Court of Arbitration for Sport which previously found the rules were "discriminatory" but "necessary" to ensure fairness in women's athletics.
The IAAF measures were previously approved by the Lausanne-based Court of Arbitration for Sport (CAS).
We are in for a major shake-up in the wake of the ruling of the highest court in sports on Olympic gold medallist Caster Semenya.
The South African, a two-time Olympic champion, timed 1min 54.98sec to defeat Burundi's Francine Niyonsaba, who clocked 1min 57.75sec and Ajee Wilson of the United States in 1min 58.83sec.
The IAAF insisted the rules were essential to preserve a level playing field and ensure that all female athletes can see "a path to success".
In a rare intrusion in the world of sport, the United Nations' top rights body has passed a resolution stating that the IAAF may be in breach of international human rights norms and standards.
In response to the report, the IAAF -- stressing it was referring in general terms, not to Semenya in particular -- denied it intended to classify any DSD athlete as male.
Supported by the South African Athletics Federation, the two-time Olympic champion in the 800m (2012, 2016) and three-time world champion (2009, 2011, 2017) has denounced the proposals.