Players in the North American League of Legends esports league have voted to walk out in protest of Riot Games’ decision to no longer require franchises to field an amateur team. Since Riot’s announcement, many franchises have already dropped their amateur teams for the summer season, cutting off an important development pipeline for players who want to compete in the main League Championship Series (LCS). The vote, held by the LCSPA, which represents North American League of Legends esports players, passed “overwhelmingly,” according to an early Monday tweet.

It’s unclear exactly when the walkout will take place, but assuming the two sides don’t come to some sort of agreement, it seems likely it will happen at the start of the summer season (also called the “summer split”) on June 1st.

Tensions over the issue have been brewing for some time. On May 12th, Riot Games announced that franchises had asked it to drop the mandate requiring them to field teams in the amateur league, the North American Challengers League (NACL), and that it would be dropping that mandate. In a statement that same day, players pushed for some kind of structured amateur competition, noting that “over 50 percent of current LCS pros came up through the NACL / Academy system” and that Europe, China, and Korea maintain competitive developmental leagues.

League players have voiced their disappointment Riot’s decision to let franchises not field NACL teams. “I wouldn’t be in [the] LCS had it not been for Academy,” Palafox, a player for NRG’s LCS team, wrote on Twitter. “The Academy / NACL system gave me the opportunity to pursue a pro career,” tweeted Chime, a player for TSM.

However, in the days after Riot’s announcement, five of the ten teams in the LCS said they wouldn’t be participating in the NACL this summer (100 Thieves, Cloud9, Dignitas, Golden Guardians, and NRG), and the LCSPA tweeted that two more wouldn’t have NACL teams, either (TSM and Immortals). Many North American esports organizations have been struggling as of late — TSM announced it would be leaving the LCS for another region, NRG recently acquired Counter Logic Gaming, and 100 Thieves laid off staff in January — and some of the statements from the franchises noted the challenging economics of having an amateur team.

On Tuesday, journalist Mikhail Klimentov reported that players would be voting on the walkout. An LCSPA list of demands for Riot Games includes a system of promotion and relegation between the LCS and the NACL, revenue pools for NACL salaries, and guaranteed contracts for one year for the LCS players that win the summer finals. On Monday, the LCSPA asked players to not cross the walkout line if recruited by a team to play as a replacement.

Riot Games and the LCSPA didn’t immediately respond to a request for comment.