Hi @tisme,
Thank you for your question about locking the tap outside of your house.
I'd suggest replacing the tap with a vandal proof tap such as this Kinetic 15mm Brass Vandal Proof Garden Tap.
They allow you to remove the tap key meaning they can't be turned on without the tap key which can be kept inside your home to prevent the tap being used by anyone else. They are often installed at sports clubs and schools where water is needed, but they don't want everyone to be able to use them.
You would need to confirm the compatibility in terms of pipe diameter and may need to install an adaptor to make it work.
If you posted some photos and dimensions of the tap, I'd be happy to assist further.
Let me know if you need a hand uploading images.
Jacob
