They can search your laptop at the border without probable cause. We know that from a couple of years ago.
But Judge O'Scannlain adds to that today. They can also search your laptop at the border without even reasonable suspicion.
Personally, I would have at least cited the earlier Ninth Circuit case, especially since it says a lot of things (albeit in dicta) that support Judge O'Scannlain's holding. If only to let everyone know I was aware of it.
On a more practical level, for you international travelers out there: Don't put anything on your laptop that you wouldn't be willing to broadcast to the world. Because the U.S. Government has the categorical right to spend as much time as it wants looking through your private stuff for anything in which it might be interested.