While I agree that you should be in the right lane while cruising a divided multi-lane highway, passing only in the left, there is no law in the books saying so.
KEEP RIGHT EXCEPT TO PASS is usually found on two-lane highways when going up a hill (turns into three lane). Not found on a divided highway. A semi, for example, would be slowing down while climbing a hill, so a passing lane (left lane) enables faster traffic to pass it, and then MOVE back to the right lane. You are required by law to do that.
Here is a prime example going east on highway 11 up the Red Deer River bank.
SLOWER TRAFFIC KEEP RIGHT is only found on divided highways. The legislation says you can travel in either lane at or near the speed limit. There is NO law requiring you to travel in the right lane only except for passing. Slow moving traffic legislation comes into play at an officers discretion. A tractor or combine should never be in the left hand lane of QEII. It is legislated to the right lane only.
Here is a prime example going south on the QEII west of Blackfalds.
If we want to get left-lane hogs out of the left-lane, then we need legislation saying so. Maybe once QEII is tripled, we might actually see some progressive laws being made on that highway regarding speeds, just like Europe.
As a common courtesy, I move to the left lane to let people on the on-ramps merge safely, as well as myself overtaking other vehicles obviously. Other than that, I stay in the right lane.