Just spit balling here but:No player will walk away from their club if they are prevented from playing for their country. They don't get paid by their country.
Anyway i don't see how legally you can prevent a player representing his country because of a decision made by his employer. It's not as though the players started the ESL.
National teams are run by the nations FA
Each FA is affiliated to Uefa and Fifa
Players aren't playing in FA sanctioned competitions
Therefore, they are not eligible to play for the national team