backflow valve question, house is bidded on!

Put in a bid on a house today, escrow states "Plumbing problems, pressure untestable," Realtor stated its backflow valve was missing, so i looked during my walk around, someone lopped it at the ground pipe (source), and both inputs, at the house, like an inch left out. they used bolt cutters, pipes clamped shut. luckily its the garage wall so i can open the wall and run new copper.

I stated it was probably for the sprinklers, and i would just sweat a new pipe bypassing the sprinklers for now, and he was quick to say no, all houses have them, and are required to have them. uhhh what? can someone clarify, in the state of az, or is it a county thing? city thing? sense when do they require backflow valves?