If ATC issues a clearance which will cause you to violate the FARs, are
you legally bound to accept it?


No.

If you are in the air, you still fly your old clearance while you reject the
new one and you and ATC work it out. If you are on the ground however, ATC has
no incentive to work it out with you. You end up staying on the ground.

Jose

--
(for Email, make the obvious changes in my address)