I thought the speed limit was the speed limit in any lane. You rarely see anyone on the highway driving UNDER the speed limit - just over it. I don't see people driving too slow as the problem - just people driving too fast. I like to drive fast as well, but not when I'm going to infringe on the right of other people who are simply following the law.
You don't need another law to combat the original laws - you just need the original laws enforced. If anything, I'd like to see a law to arrest and suspend the licenses of A-holes who drive up your butt and start flashing lights and what not because they think it's their God given right to drive like 100 mph in congested traffic and flit back and forth between lanes. These people are the real danger.