Pilots should understand that the alternatives to accepting the new
clearance are probably a very lengthy reroute, diversion to another airport,
or IFR cancellation.

....which may be better than flying into ice over the ocean. And it is
not the perogative of ATC to cancel IFR on an airplane that =already=
has a clearance, which ATC decides has become inconvenient.

The alternative to accepting the new clearance is flying the old
clearance, and ATC puts up with the consequences (which may mean that
another aircraft has a delay or a reroute). IFR is a joint endeavor,
not an ATC "take it or leave it" thing. However, if there is one who
has the "take it or leave it" perogative, it is the pilot whose ass is
in the system and already has a clearance.

Jose
--
Math is a game. The object of the game is to figure out the rules.
for Email, make the obvious change in the address.