I'm sure the US Border Patrol could find a use for full auto.
No there is not, but there are times that a rifle is needed.
Cops have carried rifles throughout the years, this is not a new thing. It's news worthy because they are "ugly guns"
They have carried anything from 22's for stray, injured animals in the country to M-1 Carbines and 30-30 lever actions for things that a shotgun is not appropriate for