CBP recently began asking foreign visitors to the U.S. from Visa Waiver Countries for their social media identifiers. Last fall we filed our own comments opposing the policy, and joined two sets of coalition comments, one by the Center for Democracy & Technology and the other by the Brennan Center for Justice. Notably, CBP explained
that it was only seeking publicly available social media data,
“consistent with the privacy settings the applicant has set on the
platforms.”

(via Fear Materialized: Border Agents Demand Social Media Data from Americans | Electronic Frontier Foundation)