You can't build on Crown land without a permit ...if it is a cabin or some other type of shelter they will tell you to take it out or they will take it out at YOUR expense!!
Crown land is just that ....it belongs to the Crown(you and me)...trust me I know, I belonged to a camp on Crown land with a 99 year lease...after the lease is over we will have to dismantle the cabin or they will bulldoze it into the ground at our expense. (I'll be long gone)
Them's the rules
Dennis