Earlier quoted context omitted.
Is it actually legal? In France, a bag in a public place is deemed to be a bomb and the military has to come, secure the area and destroy it. Happens on a routine basis, not even worth the newspapers. You don’t have such laws in Washington DC?
In the UK it's generally the same too. People are always cautious and told to look out for unattended baggage for that reason.
If the item is not hidden, not obviously suspicious, and is typical of the environment in which it was found, then it's unlikely to be a threat and can be inspected further.
Unattended bags are found all the time. There's no need for the military to be called in for all (or even most) of them. And even then, that's mostly the responsibility of the police than the armed forces.