JONATHAN TURLEY: We might need to amend the Constitution.

In my Supreme Court class, I call this a “default case” in which justices tend to run home. When a record or the law is uncertain, conservative justices tend to avoid expansive, new interpretations. That was precisely what Trump said he wanted in nominees.

These justices are not being “disloyal” to him, but rather loyal to what they view as the meaning of the Constitution. I have at times disagreed with their view of the law, but I have never questioned their integrity.

None of this means we should accept the expected outcome in this case as the final word on birthright citizenship. Justice Robert Jackson once observed that he and his colleagues “are not final because we are infallible, we are infallible because we are final.”

The final word actually rests with the public. We can amend the Constitution to join most of the world in barring birthright citizenship. There is no more important question in a republic than the definition of citizenship.

We are becoming a virtual mockery as we watch millions game the birthright citizenship system. China alone has hundreds of tourism firms that have made fortunes in arranging for Chinese citizens to come to U.S. territory to give birth and then return home.

No republic can last without controlling its borders and the qualifications for citizenship. We have allowed U.S. citizenship to become a mere commodity for the most affluent or unscrupulous among us.

One way or another, that has to change.