If your parking did not break any rules (like there was no warning sign in the carpark), you could argue that the clamping was unjustified.
If you are charged more than the maximum $100 fee for removal, you could argue that the clamping was unreasonable.
If the person who arranged for your vehicle to be clamped was not the owner of the land or business (or their employee) where you parked, you could argue that the clamping was unauthorised.