>CBP policy allows basic searches without any suspicion of wrongdoing; advanced searches require a "reasonable suspicion of activity in violation of the laws enforced or administered by CBP" or a "national security concern." U.S. Immigration and Customs Enforcement has a similar policy permitting both basic and advanced searches.

I think the argument here is that while the folks protecting the border have broad powers... they still have to be protecting the border when they use them and the "advanced" search requires some level of suspicion / reason.

If say they're sweeping up "advanced" phone data just as a policy or arbitrarily but without much reason beyond that there is an argument that would not fulfill the requirements of the law to do so.

In this case the question seems to be if the "advanced" methods are being used properly. Also there's a frequent dance with US law where powers provided to various government entities are balanced with the constitution even if the powers provided are specifically allowed.