If EJ is able to add in his contract that he must be released for the WJC, then that's good for him and his country. If not, well either he signs the countract with the club on their term or don't sign and play for the USA. He probably will sign with the club, he has no choice if he wants a professional career that will earn him lots of dough.
If I was a superstar, I would try something like that too because for me, winning a Gold medal for my country is more important than winning a Stanley Cup. Ever heard of head hunters? Some companies go the extra step to lure candidate to work for them and often times the candidates have demands and companies do give to demands of who they really want.