They do have their own laws. Every eu regulation is
1. open for veto by every EU country - so the UK could veto a new regulation
2. needs to pass by a country’s legislative - and it can be interpreted any way the country wants.
No, you’re subject to the laws of another - in this case the EU.
All the fancy footsteps to deal with one freaking regulation? Who’s going to do that with the mountains of regulations the EU has and will spew out?
Fugeddabouddit.