The whole Superleague depends on the fact that they are allowed to play in domestic leagues and that players don't get banned from international play. Those two are pretty big "ifs" to depend on when they just dropped this bomb without any notice on UEFA/FIFA, which will no question asked for A LOT of compensation.
These clubs want a more profitable and even safer Champion's League for themselves are kinda expecting the establishment to play along because they are big clubs. Well, if FIFA/UEFA doesn't agree with this, the Superleague is fukked because this shyt will NOT have a Champion's League appeal if it's the only competitions these 20 teams are playing every year. Specially by year 3 of this experiment.
As I said in another post, the only leverage UEFA and the respective FAs have against these clubs is banning the players from domestic and international play.
Some players may be upset about that, but at the end of the day, these are professionals. If they can expect a pay raise while playing increased competition week in week out in a new format, they may definitely be down for it.
People keep missing the point. The appeal of the Champions League is just that; the storied and established clubs of Europe battling it out to see who is the best. This format gives them a chance to do that, but in a more complete league fashion. Clubs are businesses. They are only members of their respect FAs insofar as they are contracted to their leagues. There is nothing stopping them from hightailing it and forming a new league. Do you really think a league of the top 20 clubs in the world will not be more watched than a league without them?