Why people can't understand that, by FIFA rules, players must go to the NT if called? When a player retires from international football, is just an agreement to not be called any more, there is nothing formal in it. Of course NTs know there is no use in calling a player who doesn't want to play anymore.
PL clubs tried to bully the South American NTs by not releasing the players because of something the UK goverment did (not the fault of south america). Brazil apparently decided to throw the rule book on them. Maybe a bit childish, but entirely their right.
Brazilian players wouldn't have needed to isolate when entering Brazil, that rule is for foreigners
I don't think this will be a problem with Cavani, he wasn't called up by mutual consent (Cavani and the NT agreed is what better not to comer)
This is all FIFA fault for not acting before hand to stop this situations for happening... PL clubs, players and NTs are just try to defend their interest as they can