"birthright citizenship is unconstitutional" is a terrible way to frame it. I hope that's what his lawyers say when they get heard in court.
I had previously believed and said that the courts are just going to slap this thing down and Trump was going to be able to say the did his part and it would end there, but I am feel less sure. I'm going to tread weird ground here, so I'm writing a preamble. I oppose this. I oppose it because it is a tentpole in a campaign of racial scapegoating that will cause and exacerbate a lot of social problems in our country. Much bigger problems than the ones it seeks to solve, so we would be better off just leaving it alone.
I begin to believe this is really going to pass. Most discussion I see acts like it puts everything up in the air, but the EO is pretty precise. I wouldn't have been surprised if they had looked for a way to unto Obama. But perhaps they did look and his case was really too solid. The EO only excludes people who were born in the US with neither parent a citizen or legal permanent resident. If that were how the 14th Amendment had said it, I am very doubtful that people would openly argue now that the rules should be changed to include children of people who snuck over the border.
When the 14th Amendment was written, no one was sneaking in because no one was being turned away. The writers would have had no concept of this application. If it were being decided by REAL strict-constructionist (it won't be) the snag would be that the Amendment was not intended to address this topic at all. The people it was written to make citizens were born to legal permanent residents. The strict-constructionist would have to say that nothing in the Constitution addresses this and Congress needs to write a law or Amendment. But I don't think we have any strict-constructionists on the Supreme Court. They will decided this according to how they believe it should work in the present and I don't know exactly what any of the justices think about this, but 6-3 gives Trump a margin for surprises.