Birthright Citizenship Again

The Supreme Court has decided to rule on whether Trump can modify Birthright Citizenship through executive order. I have a bad feeling about this.

If a president can declare a portion of the Constitution null and void, or declare there are exceptions to it, then of what use is the Constitution? 

Yes, I understand the "subject to the jurisdiction thereof" arguments. But the phrase simply means under the authority of U.S. law. It therefore excludes foreign rulers, foreign diplomats, people on board foreign ships and foreign armies. At the time it also excluded the Native American tribes. 

Immigrants, both legal and illegal, are under the authority of U.S. law and therefore "subject to the jurisdiction thereof." That fact that US authorities can arrest and imprison an illegal alien for committing a crime demonstrates that. There has never been any doubt about the meaning of this phrase. There was no doubt about it when the Senate debated it, and no doubt about it when the court ruled in US v. Wong Kim Ark. 

If the court allows Trump, or any other president, to modify the meaning of the Constitution then the Constitution would be in serious need of defending.

This SCOTUS is already going to go down as the worst, most boot licking court in history but allowing an executive order to modify the meaning of the Constitution would be a violation of their oaths.