Not really.
All you have to do is get rid of all the red dust around the door, and place a switch to open it.
Yeah what part of "can't destroy" don't you understand.
Also, you're still stupid.
Place it so that when it is powered, it is closed. Now when they make a switch to open it, all they accomplish is locking it.
Then design your mechanism so the redstone can only be destroyed from the inside. Which is pointless BECAUSE YOU CAN'T DESTROY OTHER PEOPLES STUFF IN A CLAIM FLAG.