The problem is that such 'review' can be irreparably damaging to a number of companies, persons, etc. It's not that the government doesn't have the power of such changes of policies, it's that they could be damaging regardless, especially when they're unannounced and impossible to plan for. So the government might be within it's right, but that doesn't mean it's order is not damaging, and will have to respond for that damage. After all, it was the same government (regardless of the change of administration) that made assurances, through visa papers (which have expiration dates, and certain rules for revocation), that those persons were en led entry into the US.
In other words, a lot of this could've been avoided if handled differently: Should the government would've announced a review of all visas starting at a certain point, or not denying entry while such review process was ongoing, or decided to stop issuing visas until that process was complete, etc... this probably would look a lot different now.