It's not hard to justify wasteful expenditures already, I don't think this would do it. On the other hand it's not illegal to carry a weapon (per state laws aro

It's not hard to justify wasteful expenditures already, I don't think this would do it. On the other hand it's not illegal to carry a weapon (per state laws around permits for concealed/open carry) and many people routinely do so, so if this were deployed on a wider scale they'd already detect enough people to make stopping each of them pretty time consuming. But from the article it's currently going to be used in "mass gatherings like concerts, malls, stadiums, public transit stops and government buildings" which may have individual rules against carrying and so you can treat this as better enforcement (though existing government buildings' metal detectors and x-ray machines for bags seem to be doing just fine). The more interesting application is combining it with facial recognition. You don't need to approach everyone this system detects, but you can then keep a closer eye on them throughout the duration of the event/their presence in a location. It's just another step in the ongoing and ultimately futile efforts to eliminate lone wolf attackers while continuing to turn a blind eye towards organized crime. It's not just the scanners people aren't going to be able to stop.