This seems more like a Fourth Amendment issue, pertaining to unreasonable search and seizure. It's also a Customs and Border Patrol policy that has been in place since 2009, although implemented with increasing frequency in 2015, 2016 and 2017.
Given that the Knight First Amendment Institute at Columbia University is exploring this topic, is this CPB practice considered a First Amendment violation? If so, what's the specific legal argument? For additional info, see: https://www.propublica.org/article/can-customs-border-protection-search- phone-legal-rights
