That’s not specific to having a constitution. Judges in the Netherlands for example also cannot do a judicial review to determine the constitutionality of any passed laws. And that’s with a written constitution. There’s also no supreme court. The closest thing is the Raad van State (the “state council”), which evaluates all laws on proportionality, constitutionality, and executability, and then advises the government what to do with a law. It’s convention that that advice is followed, but it’s not required.