If that is what you or the people of California believe, they can take the US to court. They can convince other states to join them. But that isn't the argument they are making. Frankly, pursuing that line would lessen their already minimal chances for success.
That only works if the courts will hear the case. There are a few other constitutional issues that the federal courts refuse to hear. What should people do then? Can a state court declare a federal law unconstitutional?