If the person registering the car is not the owner and they "click" they are attesting as to who they are - if the car was owned by the decedent it is under the purview of the executor/administrator and it is that person's job to take responsibility for it. It also needs to be insured so someone has to be responsible for that.
This is not legal advice nor intended to create an attorney-client relationship. The information provided here is informational in nature only. This attorney may not be licensed in the jurisdiction which you have a question about so the answer could be only general in nature.
No. Here's the deal. If you (or the Personal Rep) has questions about this simple issue, then there are a dozen other legal landmines that he or she needs help with. Get an attorney to help administer the estate.
To quickly answer this question, the car still belongs to the deceased person's estate. No one is entitled to drive the car. (I am aware that sometimes a car may need to be driven a short distance to be stored. However, technically that is not permitted either. The options for the Personal Representative are to (1) sell the car or (2) transfer the car to one of the beneficiaries. This is more complicated than I have time to write about. The Personal Representative needs to talk to an attorney.
If you retitle the car to your name, it is theft. Don't do it. And contact an attorney. Especially if the family is fighting.
Please note that I am answering this question as a service through Avvo but not as your attorney and no attorney-client relationship is established by this posting. An attorney-client relationship can only be established through signing a Fee Agreement and paying the necessary advanced fees.
each state is different, so you'd need to look at Arizona's statutes/laws and/or ask a Az lawyer, but if i were you, id be very hesitant to do this, it is very likely a crime or at the very minimum not allowed.