> The interpretation of existing jurisprudence is that age limits on the free exercise of rights is Constitutional in many circumstances regardless of if such limits are not explicitly in the Constitution. This is a simple observation of the current state of reality.

> Those age limits are arbitrary and the justification can sometimes be nebulous but they clearly exist in the US.

I mean, kind of, I guess?

States make their own age-related rules. The states are part of the US. So technically sure, you're right. In practice, you're very wrong.

> States make their own age-related rules. The states are part of the US. So technically sure, you're right. In practice, you're very wrong

This is wrong. It's particularly wrong in the way that you draw a distinction between theory and practice. It's so wrong that it's backwards.

In theory, the states set age related rules. In practice, they must set them to what the federal government tells them to. This was established in the specific case in 1984 [0] when Congress realised that it could withhold funding to states based on how quickly they agreed with it, and in the general case in 1861 [1] when the United States initiated a war that would go on to kill 1.6 million people after some states asked it only to exercise the powers derogated to it in its constitution.

[0] https://en.wikipedia.org/wiki/National_Minimum_Drinking_Age_...

[1] https://en.wikipedia.org/wiki/American_Civil_War