The problem isn’t necessarily the ECHR; it is how it is interpreted and implemented by the courts.
This isn’t a case of parliament not being sovereign, it’s more a reflection of how it is impossible for Parliament to define every possible variation or outcome.
It’s similar to the current problem of defining a “substantial meal” - is it a scotch egg, 2 scotch eggs or 2 scotch eggs and a bowl of chips? Ah, but what about falafel and salad? Or how about a ploughman’s plus soup-in-a-basket?
A pub serving a pizza and 12 pints doesn’t represent a challenge to Parliament‘s sovereignty even if it’s against the spirit of what Parliament intended.
the EU would issue an EU directive, specifying 2 Scotch Eggs, where they must be made, the weight in Grammes, the thickness and shade of brown for the crumb Coating.