Traditionally, the law has been that searches at the border are plenary and require no suspicion at all — they are reasonable because they occur at the border and because a sovereign has control over goods and people who enter or exit its territory.
Cotterman rejects that general rule. It concludes that given the comprehensive and intrusive nature of searches into the contents of laptops the government must articulate a “reasonable suspicion” before it may search the contents of a computer system.
Source: Lawfare. Read full article. (link)