The company is responsible. Waymo should get the citation.

Arizona law does allow officers to give out tickets when a robotaxi commits a traffic violation while driving autonomously; however, officers have to give them to the company that owns the vehicle. Doing so is “not feasible,” according to a Phoenix police spokesperson

I'm not sure why the police say it's "not feasible" to issue Google a citation. Google are the registered owners of the vehicles and thus responsible for any actions it performs, just mail them a ticket?

I’m just speculating, but there is probably a very efficient workflow for sending a ticket to an individual (given the number of tickets written and the revenue it generates), and I wouldn’t be surprised if the workflow doesn’t accommodate an AI operated vehicle. Kind of like how a restaurant would need to restructure its workflow to accommodate DoorDash.

In other words, “infeasible” actually means “would take extra effort”.