I think if a tour pays a guaranteed salary to its players, then they can reasonably require its members to show up for X high percentage of their events, etc.I agree to a point. What about contractual duties? If a player signs a contact saying this or that aren't they bound by it? I have no clue what's in a WNT player's agreement. I don't think they care where their stable of players play as long as they show up for the WNT events deemed part of the agreement.
The way it is now, with the only carrot being the prize fund, I don't think any tour should have exclusive control over any player.
At least the way MR is doing it is far better than WPA. They are basically saying "show up for our big events, and do whatever you like the other days, including playing for the competition".
WPA is saying: "You can ONLY play in our events, no matter what".
If this stuff ever gets to court, I think it will go the way of "non-compete" clauses in the dayjob workplace. I believe most of them have been stricken down on the grounds of "my employment choices can't be limited in my area of expertise". There is probably no area of expertise in any day-job as explicit as a professional athlete in their specific sport.