If I'm driving the speed limit in the left lane, and you want to drive 15 MPH over the speed limit, you are welcome to drive around me.
Fine with me as long as you at least move over for faster traffic otherwise you are just causing a chaotic bottleneck behind you.
I pass, get in front of the slowpoke and then slow down to 45 mph because that's legal too... used to do it to Priuses out in Marin County quite often. ;-)
In most places you are free to get the hell out of the way. Left lane is for passing, and that’s IT. Not for cruising. You can cruise in it if you’re not obstructing others passing, but as soon as you force others to go around you become the jerk because in many place passing on the right is illegal, get out of the way and let them pass on. Don’t worry about if they’re breaking the speed limit, that between them and the next cop down the road, just be courteous and move the hell over.
Basic courtesy and overall safety would tend to dictate following these simple rules:
Slower traffic keep right, and
The faster car goes in front
If a person wants to drive exactly the speed limit in the left lane, that’s fine, as long as he/she has the courtesy to move over and let faster vehicles pass and has the awareness to check his/her rearview mirror on a regular basis.
I’ve been on the highway between CA and AZ plenty of times with my cruise control set at about 5 mph over the posted limit and changed lanes to let others pass me going about 85 or 90. They’re faster so they go in front of me. Then everyone’s happy and they can be the volunteers for speeding tickets.
It's illegal to pass on the right, and in a growing number of places it's illegal (and bad driving etiquette EVERYWHERE) to hang out in the left lane without actively passing.
Obey the law and get over to the right.