If it was a legitimate search with real public security purpose, there is no excuse for letting him go without completing the search.
If it was not a legitimate search with real public purpose, there is no excuse for the threats or retaliation.
Irrespective of the legitimacy of the search, the behavior here is unjustifiable.
* It was a legitimate search wrt information available at the time, and then more/better information became available, and it was no longer legitimate. (Assuming a certain definition of "legitimate".)
* It was a legitimate search, and cloning and/or compromising the devices took time.
(Just devil's advocate, for intellectual curiosity, not disagreeing with public interest concern.)
> CBP officers searched Dr. Gal’s wallet and all his luggage, and asked questions about everything they found. When they discovered Dr. Gal’s Apple-issued electronic devices, the officers first asked Dr. Gal to pull up his itinerary on his mobile phone, and then to hand the unlocked device over to CBP. Dr. Gal responded that he would email them the itinerary, but that he would need to speak with a lawyer and his employer before giving CBP officers full access to his mobile phone.
...
> Moreover, there was no reason for any CBP officers—TTRT or otherwise—to detain and interrogate Dr. Gal or his devices. Notably, CBP officers did not confiscate and retain Dr. Gal’s devices, which they were authorized to do under the Directive and presumably would have done if they truly felt that they possessed a basis for detaining Dr. Gal or keeping his devices. See Directive, § 5.3.3. Instead, CBP officers proceeded to demand that Dr. Gal provide immediate, unlimited access to his devices.