I'm not asserting that this will be mandatory, nor confirming it would violate any constitution, but countries do violate their own laws, including constitutions.
Discussion
Yes, they do. That's why Constitutional Courts exist, to enforce compliance with the Constitution.
But courts, including constitutional courts, are not perfect and are part of a system which isn't perfect. They may reach wrong conclusions and even when they get it right it may take a long time before they are even asked to decide about something.
You are right, but here in Portugal the Constitutional Court usually get it right. 😃