https://en.wikipedia.org/wiki/European_Communities_Act_1972_...
British Ministers have spoken repeatedly about their frustration at finding out they cannot implement law changes wanted by their constituents because they conflict with EU law.
Yes, the European Communities Act can be repealed at any point as part of the process of exiting the EU. But until that happens, EU law has primacy over Parliament's own laws both by widely held legal understanding and social convention.
To reinforce it one more time: by your logic everyone is sovereign and can simply choose to ignore the state at any point. It's an intellectually useless argument because it ignores the behaviour of the courts, the existence of laws stating the opposite and the ability of the state to force you to comply (which may in fact be via fines rather than jail sentences).
Likewise, any UK Parliament can revoke any law, including the European Communities Act, if Parliament wishes. In which case from a UK legal standpoint, the UK would cease to be a member of the EU regardless of what the EU might think. From a UK point of view, invoking Article 50 is the polite thing, not a legal requirement.