[StillBored]

Its not against the law in any US state (a quick search seems to back this up) to pass on the right. With one huge gotcha, it must be "safe" defined in various ways.

OTOH, most states have a stay right except to pass, slower traffic keep right laws.

Which means, that unless the person to your right is weaving through traffic, driving on the shoulder, or a few other bits of unsafe behavior, if someone passes you on the right your likely the one violating the law by not moving right when your not actively overtaking/passing someone.