Then why not have the warrant ready to go when he crossed the border? If the suspect was already under investigation and there was suspicion there would be evidence on the laptop, then it would seem a warrant would be easy to obtain. Then this would be a non-issue.
I'm guessing that this wasn't the agents' understanding of the process. From reading the opinion, it seems that they thought it was perfectly fine to search the laptop on spec, then later apply for a warrant to justify what they found.
They had enough warning that he was going to be going through customs to decide whether to grab the laptop when he arrived in the country or when he left it, opting for the latter, so yes, they would have had plenty of time to apply for a warrant if they thought they needed one up-front.
It's not that they thought it was fine to just search the laptop; that it was fine for them to seize the laptop, remove it from the scene, and then search at their leisure. It would be like border agents seizing a car crossing the border, towing it to another location (leaving owner behind as well), and searching it later. How that comes off as a reasonable search to anyone is beyond me.
