A brief follow up to the snagging post:
I spoke with a local Conservation Officer yesterday at work, and discussed the whole lip and mouth issue. His interpretation of "in the mouth" was on par with my mine: the inside of the lip would be considered in the mouth; outside of the lip would be considered a foul-hook. He understood that the radial nature of the lips on many sucker species could present a gray area of interpretation, but if the hook was embedded on the "tip" of the lip there would likely not be an issue. If the fish was able to close its lips and the point of entry of the hook/fly would be concealed, it would be a fair catch. From a legal standpoint this would all be inconsequential if you are planning on releasing the fish.
The grim reality is that the general consensus of the public is these underutilized "rough" fish do not hold as high a regard as game fish species. A citation would likely not be as readily issued for "snagging" rough fish compared to game fish, and a judge would likely not hold the same gravity on the case. Technically, there is very little protection offered these fish under MN statute and rule so it is not the judicial branch's fault for treating cases as such.
Ultimately, it is up to each angler's own conscience to determine if a fish was fairly caught. For all us roughfishers' sake, let's not cheapen the sport and our accomplishments by counting a snagged fish as caught.