It will be affiliation, so self registering on GMS the same as it is for age grade, the onus is on the players to do it themselves, and renew to every year. Age grade players can be affiliated (although they are renaming this back to registration) to multiple clubs, this was the question for adults - it seems that it will be one club only, like effective registration (Adult league players).
I speak from experience, that even when GMS is working (currently a lot of parents can't find our club in the system and actually affiliate their kids), people struggle with it, and won't do it - so can't play :-(