You aren't allowed to use them if they didn't come with your boat. If you have an old boat that came with them, they are legal for use on that boat - you can not get an old boat with wood blades and then transfer the blades to a new hull.
Yes Dave is right. I still have the original wood rudder that came with my 1979 laser. It is legal to use wood foils if and only if they came with your boat. If you have wooden blades its a bonus. If you take good care of them, they're supposed to be faster than glass ones.
If the rudder had less rake it would be more efficient but have less feel. The rudder is fine as an aid to steer the boat provided you heel the boat first. The rudder is not big enough to over come a poorly sailed boat.