They can be subject to criminal penalties but they can’t be drafted or serve on juries because they’re not citizens and therefore have no allegiance to the US. At least that’s the interpretation of the jurisdiction clause that many experts believe was meant when it was written in the 1860s.
See posts 82 and 83 for the best legal take on it that I have come across.
Wow, thank you for posting that. I learn more stuff here on FR!