If the warnings are part of the culture, they are superfluous; cops should not need to recite them of everyone already knows them by heart. Yet, somehow, the Court used this fact to come to the opposite conclusion. This is example #1,817 of the Myth of the Rule of Law. The Court is almost entirely a political creature.
As for the birthright citizenship case, legal reasoning has little to do with it. Paraphrasing Beria, show me the desired result and I’ll find the reasoning. And I think we all know what the desired result is.