Since the founding of our Republic, Congress has granted the Executive plenary authority to conduct routine searches and seizures at the border, without probable cause or a warrant, in order to regulate the collection of duties and to prevent the introduction of contraband into this country.
In this case a standard of suspicion is set before border guards can detain someone for hours hoping their bowel movements might produce cocaine balloons. That standard is very low, but there is a standard. It cannot be done at random. The question is whether a search of a laptop's contents is "routine" or whether it is special. Note Brennan and Marshall's dissent, which is much more along the lines of my thinking then the majority.