How, exactly, is a developer supposed to change state in a stateless protocol to denote that you've dismissed the cookie dialog if the user has disabled the feature that allows the developer to add state to the stateless protocol?
It's not hard. It's just a matter of checking for navigator.cookieEnabled.
It also highlights how, in general, this is a hard problem. Compliance with this law without creating a dead-static page has subtle complications.
But on the top of my head only display the dialog if the browser cache is cold. Could embed a timestamp in some cachable resource. (Edit: Perhaps this counts as a “cookie“ in the legal sense)