Not only does the Chruch book state it is prohibited to park along the highway right of way, but so does the Milipost guide. A couple of years back, a few of us forum members spent some time trying to research the matter with no success. It almost appears to be one of the myths that go along with the Alcan/Alaska Hwy. you know many of them, from the road will tear up your rig ( no, the rig driver will tear it up if they don't have good driving skills) to you need several spare tires, etc. Repeating and believing these myths, seems to make some first/second timers feel more macho and adventuresome .
Bottom line is, we couldn't find a law that even spoke to the subject, if not road signed, no one on the forum has ever reported being told to move by law enforcement. Just get well clear of the road and don't block someone's drive way.