Here's what the law is about. If you see that an emergency vehicle is stopped on a highway, you must, if it is safe, change lanes and move into the next adjacent lane that is away from the stopped vehicle. It doesn't matter whether it is on the right or the left. You must move into the lane away from it. As of 2011, the Move Over Law also applies to tow trucks or any vehicle with hazard lights flashing.
So, let's say you have four lanes of traffic moving along I-10, and you are driving in the right lane. You see an emergency vehicle parked on the right shoulder. If it is safe to do so, you must change lanes into the next left lane to you, so as to leave an empty lane between you and the vehicle. What if there is only one lane on the highway that you are driving on? Just proceed slowly in your lane until you are safely past the stopped vehicle. What if there are more than two lanes, but you can't move over safely? Again, just slow down and proceed in your lane with caution until you are past the stopped vehicle.
Contrary to some emails that are circulating and some rumors that are floating around, this law does not require you to move into the far lane of the highway. In other words, if there are four lanes moving in your direction and a DPS officer is stopped on the right shoulder, everyone doesn't have to move over three lanes into the far left lane.
You can read the official statute here. Failure to comply with the Move Over law in Arizona could result in fines as well as points assessed to your license. It is a moving violation.
Laws are subject to change without notice.