totally in your right to take it off from private clamper and private land, i had the same trouble at the rally of the lakes two years ago, at the time id didn't know how to take it off and my friend did it. the guards were called out to the b&b i was clamped at saw the clamp on the floor and they didn't say a thing took my name and then searched the car .
iirc the land owner wanted 160 euro