Cricket is just another profession. The top players receive millions of USD every year from the IPL. They get less than 5% of that amount from the national cricket boards. So why should anyone be forced to play international matches against their wishes? If the national board wants that player to prioritize the international duties, then they should match the fees that is being offered by the IPL franchises. On one hand they want the players to play for such a pittance and on the other they want them to be available all the time. This will only result in players retiring from international cricket.
This logic is not going to be acceptable for any Board even they are taking some good amount from IPL every player is surely going to accept national duty as a priority because they have this just because of their country and money is never been a priority for many players just very few can go with this logic but mostly still will prefer national team on this IPL because here they have just one or two seasons and the national team is surely having some good long time for them.
Hopefully, in near future, we will have some better laws about this because no board will give this acceptable even they are making some good money from IPL if we have any confrontation in this than most boards will try to ban their players from joining this IPL because with this it's going to be a bad impact on this game. Sometime back same issue happened in soccer then FIFA gives a ruling in favour of countries, so I feel most chances this will happen here as well.