Valve has warned tournament organisers and teams that exclusive leagues could cause "long-term damage" to professional CS:GO.
In a wide-ranging blog post published on Thursday designed "to make sure everyone is on the same page", the game creators said it welcomed new tournament formats and ideas but warned against teams becoming over-committed to specific events.
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The statement follows the announcement of the ESL Pro Tour, due to launch in 2020, and Astralis' apparent commitment to BLAST Pro Series.
Valve said: "We make it free to get a licence to operate a CS:GO tournament because we want to get out of the way of third parties creating value for our customers.
This form of team exclusivity is an experiment that could cause long-term damage
"Often that value comes from experimentation tournament operators experiment with presentation, technology, formats, locations, etc.
"We support experiments that are scoped large enough to identify new and interesting opportunities, but not so large that if they fail it would be hard for the ecosystem to recover.
"Recently there have been steps toward a broad form of exclusivity where teams who compete in a particular event are restricted from attending another operator's events. This form of team exclusivity is an experiment that could cause long-term damage.
"In addition to preventing other operators from competing, exclusivity prevents other events from keeping the CS:GO ecosystem functioning if an individual event fails. At this time we are not interested in providing licenses for events that restrict participating teams from attending other events."
Valve also used the blog post to remind teams and TOs of its stance on conflicts of interest in CS:GO.
There have been some concerns over the link between Astralis and RFRSH, the company that runs BLAST Pro Series. RFRSH announced in July 2019 that it had sold Astralis to a separate entity, though some remain sceptical about the arrangement.
On shared ownership, Valve said: "We consider a conflict of interest to be any case where a tournament, team, or player has a financial relationship with any other participating team or its players. This includes multi-team ownership, leagues with shared ownership by multiple teams, or essentially any financial reason to prefer that one team win over another.
"In open events, like the Majors, teams with these business arrangements may have (real or perceived) financial interest in the success of teams that they are competing with.
"In order to participate in Majors, we require that players, teams, and tournament operators confirm that they have no existing conflicts of interest, or if they do, disclose them and work to resolve them.
"This requirement isn’t new, but we felt it was worth reiterating given the conversations we’re hearing. If you are interested, the exact terms we require are below."
Pictures: Timo Verdeil, Bart Oerbekke, Adela Sznajder / ESL