Our bonus policy was like this from the very beginning already for about 8 months and no one had a cancellation problem before.
My is bigger and fatter:
Your Balance will be locked while bonus is active. You can cancel bonus at any time.
Bonus must be wagered 55x to became a part of your balance.
You don't have right to take balance from anyone who cancel bonus.
It's clearly stated in YOUR bonus rules.
Why don't you return stolen money?