It centred around whether World Aquatics, then known as the International Swimming Federation (FINA) were engaging in anti-competitive behaviour when it declined approval of an ISL and USA Swimming event in 2018.

ISL - and a separate lawsuit filed by American swimmer Tom Shields and Hungarian swimming great Katinka Hosszú - used the Sherman Antitrust Act of 1890 in their respective cases.

Although the US District Court admitted it did not have experience in monopoly disputes in international sport, it concluded FINA declining to approve the event was "reasonable" to avoid a clash with its own events.

Judge Jacqueline Scott Corley added anti-trust laws do not require one competitor to accommodate another competitor, only prohibiting "unreasonable restraints of trade".

"World Aquatics is grateful to Judge Corley for her thoughtful and just decision," said World Aquatics President Husain Al-Musallam. 

"We are pleased that it brings an end to a period of uncertainty and we are thankful for the clarity that the Court's decision provides.

"This is an important decision and also a good decision, not just for World Aquatics, but for the Olympic Movement and beyond."

Furthermore, the Court said top swimmers were not bound to contracts to swim only in FINA competitions and that the governing body for swimming did not have rules that would punish athletes for choosing to compete in ISL events.

"This was, and always has been, an avoidable controversy," said World Aquatics executive director Brent Nowicki. 

"We look forward to putting it behind us, as we look forward to delivering an exciting calendar of opportunities for all aquatics athletes, to whom World Aquatics remains deeply committed."

ISL and World Aquatics have been in a quarrel since the formation of the professional swimming league. 

When he became President of World Aquatics in 2021, Al-Musallam said he was "very open" to talks with the ISL, following years of disagreements between the parties; providing they "meet basic conditions", adding that there must be "constructive suggestions".

"There must be total transparency, with all competitions taking place under FINA regulations approved by all FINA's stakeholders," added Al-Musallam when speaking exclusively to insidethegames.

"WADA (World Anti-Doping Agency) and FINA’s Anti-Doping Code must be adhered to at all times.

"There must be no discrimination between athletes, with a system that gives all athletes the opportunity to participate at the events.

"Finally, clubs and National Federations in every country must be protected."

This breakdown in discussions led to the International Swimmers' Alliance calling on both groups to get to the table again, criticising the lack of "meaningful" consultation with athletes over a growing "unsustainable" calendar.

Between 2022 and 2025 there is to be four World Aquatics Championships, while the ISL is expanding to a six-month calendar.

On top of this, other major competitions such as the European Championships and Commonwealth Games have to be factored in too.

The 2023 ISL season was cancelled due to the invasion of Ukraine by Russia, due to its funder and founder, Konstantin Grigorishin, being involved in the Ukrainian energy sector as the head of Energy Standard Group.

The ISL is to be suspended until further notice as a result.