This problem is really hard to solve with technology, which is why either the legislative or the courts have to do their job (and need to be prodded to do it).

This problem is really hard to solve with technology, which is why either the legislative or the courts have to do their job (and need to be prodded to do it). Specifically, it's not enough to hide your social media accounts/photos/calendar/contacts from your phone. That's so obvious, they'll simply treat it the same as denying to give them your password. So what you'd need is a set of completely innocent accounts. Yet faking a complete online presence, and doing in a way that a smart algorithm doesn't notice, is almost impossible. Two more problems with some proposals that I've heard so far are that (a) they would require a significant fraction of travellers to use so as not to the few that do suspicious and (b) the drastic power imbalance at the border–people are willing to endure a lot to avoid being send back on the same plane and ruining their holidays. I also have problems understanding the doctrine that renders foreigners basically unprotected at the border. If "all men are created equal" and the Bill of Rights only enumerates natural law that exists before government, should those not apply to non-citizen?