Did you know its legal for customs to look through your phone?

Are we in Orwellian territory yet? A scientist who flew to the states to be at a science conference was denied entry for having negative emails about Trump on his phone. Before it could be investigated he was flown back to France to cover their butts, no doubt. My thing, is when did it become legal to search private information?
It seems as well it has become illegal to criticize the Trump and or the administration or the US.
With these kinds of things going on, it begs for criticism. I’m sure as a scientist, he thinks negatively of an administration that abhors science and education.