Quote Originally Posted by lisvaneblue View Post
Most of the key things related to control of infectious diseases are covered in the Public Health Act 1984, covering England and Wales
The powers are very wide ranging indeed, and I would guess includes the equivalent of what we call lockdown, although I haven’t read the detail of this very large act
It doesn't have the range of powers enabled by the The Coronavirus Act 2020 (Commencement No. 1) (Wales) Regulations 2020.

So Wales could not lockdown until Westminster decided.