UPDATE 9/10/15 11.45am: Marketplace website G2A has hit back at League of Legends studio Riot for banning its eSports team sponsorship.
In a new statement published by PCGamesN, G2A states Riot has "launched an aggressive attack directed towards the entire global e-sports community in a failed attempt to dominate and control the industry.
"[The ban] has the ability to impact negatively on e-sporters, especially during this fabulous time when hopes are so high for great e-sports events."
The ban followed a "friendly" discussion with Riot that was only met with "more and more demands", G2A claims.
Riot's beef with G2A stems from the sale of levelled up League of Legends account, something which is against the game's terms of service.
In other League of Legends news, BBC Three has announced it will livestream the game's 2015 World Championships event set to take place at Wembley.
ORIGINAL STORY 7/10/15 10.05am: A dispute between League of Legends developer Riot and popular video game key selling website G2A has spilled over and onto the eSports battlefield.
As reported by The Daily Dot, Riot banned G2A from sponsoring League of Legends professional teams, including Cloud9, Counter Logic Gaming and H2K, and removed the website's logo from merchandise available at the 2015 League of Legends World Championships.
G2A came under fire because it contains a listing on its website that promotes services from a third party that sells League of Legends accounts, and because it offers "elo boosting services" - both of which contravene the game's terms of service and its eSports rulebook.
At the time of publication, a number of League of Legend accounts were available to buy on G2A. One, a level 30 account, was going for $25.
Elo boosting sees a player (The Booster) log into another player's account to improve its match-making rating (MMR). It's big business, and a quick Google search shows many websites offering similar services.
Riot hates Elo Boosting because it messes with its match-making system, which is designed to get players together with those of a similar skill level.
"If a player's MMR is boosted unnaturally they will most definitely falter when they begin to play ranked at that tier," Riot has said. "If a player is unable to keep up with the other higher MMR players in their match they will most certainly degrade the game experience for everyone involved."
In a post on the League of Legends subReddit, Riot's developer relations manager J. Eckert confirmed Riot had banned G2A as a sponsor on 18th September after negotiations with the company failed to come to a resolution.
Here's the post
The ball now appears to be in G2A's court. We've asked the company for comment, but The Daily Dot reports G2A has told professional teams that it intends to drop sponsorship across the board following the ban.
There is also the issue of G2A sponsoring streamers. A raft of popular Twitch streamers, including those who play League of Legends, are sponsored by G2A. Will Riot turn its attention to those, next?