If you are in a place and you have permission to be there, you can use reasonable force to stop someone from entering that place without permission. You can also use reasonable force to remove someone who is already in that place without permission. However, you must not hurt that person or cause them bodily harm.

You are allowed to defend the place if you are the owner, or if you are helping the owner, or if the owner has given you permission to be there.

The law says you can use force to protect the place, but you must always try not to hurt anyone.