Re: NZ and territories
It's illegal to pull into the left-hand lane to overtake, but if you happen to already be in that lane when you encounter a middle-lane hog trundling along below the speed limit it's perfectly legal to continue at your speed in the LH lane and pass them.
That's debatable...
What the Highway Code allows is to pass on the left when the vehicle you are passing is turning right, or when traffic is moving slowly in queues. That's poorly-defined; your definition *might* work, or it might not.
Then again, I once had a copper pull alongside me (I was doing 70 in the LH lane), brake, and then claim I was trying to pass him on the left. It's the luck of the draw, I guess...
Vic.