By 1400, Wales had been absorbed into England, and came under English law. Trouble was, Welsh law was dramatically different, and so there was a lot of confusion and argument. And that’s before Scotland got into the mix…
No wonder things got complicated. Three completely separate societies trying to operate under a single legal code is hardly a recipe for success.
OK, I’m pretty sure that England had sheriffs and the like before 1400.
Sheriffs were general representatives of the Crown. They enforced the will of the courts and the state, but much of that will was still in the form of uncodified common law crimes. Some statutes started getting written from the Norman Conquest onward, but these tended to pertain to property rather than criminal law.