But The FA isn’t a league, it is the sports governing body in England.Which means closed leagues aren't really the problem.
In theory the whole of the FA is closed, because if I remember the rules correctly, teams in the FA cant play UK teams that aren't in the FA.
There’s nothing to stop a team playing in an unsanctioned match, but I think they would lose insurance and anything else that their membership of The FA would normally entitle them to. The FA also wouldn’t be able to take disciplinary action against players, and there would be nothing to stop banned players from taking part.
Unaffiliated leagues are where a lot of the thugs who have sine die bans go, because they can’t play for an clubs registered with The FA.
It is the same if two teams from different leagues just decide to play a friendly, they can both be registered with The FA but if the match isnt arranged correctly it is still unsanctioned.
As a referee if I officiated in an unsanctioned game I wouldn’t be entitle to insurance for myself or my kit, wouldn’t get any support from my county FA if anything happened I.e I was assaulted, and I could also get fined and or banned from officiating.
The fact The FA don’t make any money out of unsanctioned matches has absolutely nothing to do with it...