Oh baloney! There is absolutely nothing in the Constitution that says the U.S. government can't pass a law making it a felony to illegally enter the country. Also, the law is directed at all illegals who have been deported, not just those from south of the border. In the 92 years since that law was enacted, the majority of people who were deported were Europeans -- for example, Italian nationals who were members of the Mafia.
This ruling was about reentering after a person was already given an expedited removal. The second time they enter they get charged with 8 usc 1326 which is reentry after being deported. I agree that it is a ridiculous ruling just wanted to clarify that it is about reentry not the initial illegal entry.