Don't know about down there but up here it is better to do and ask for forgiveness after. Atheist this way it gets done.

Here it is mutual agreement on the contract.If both the client and trapper agree to the trapper returning the impoundment to natural flow there is a fee.
Every client except Ontario Power Generation will let the trapper remove the dam,and unless it is an unsafe situation to the trapper,like inside a long small culvert only accessable from the low side,most trappers will do the dam removal.
OPG had problems with their union for contracting out the dam removal.
So when I issue the contract I make sure they dont mess with the dam until the trapping is completed.