In practice police do not pursue charges for marijuana possession unless it's bagged for retail. The general idea seems to be, that you can do what you want in the privacy of your home, but smoking marijuana is not socially appropriate.
It's not actually the law that's the problem. We have had ballot measures to legalize the retail of marijuana, and so far the public opinion seems to be against it. I gather that people are more or less happy with the situation as it is.
You may be confusing the law for something that actually exists, when in reality, and especially in Alaska, the question is merely what category of offense may provoke an officer to arrest you. I cannot admit to having practical experience growing, buying, and selling marijuana, nor tell of any experience that I have had in conversing with uniformed law enforcement officers about said activities. However, another person of my acquaintance suggests that marijuana use and trafficking is widely tolerated. Another person of more distant acquaintance had the curious story of having had much confiscated growing equipment returned to them out of police custody.
It is very important to note that Alaska, being in the northern latitudes, has most of its population in areas which receive less than 5 hours of daylight at the solstice. In humans lack of exposure to daylight is known to produce vitamin D deficiency, which can result in depression among other symptoms, and this disease is both prevalent and largely untreated. This to my mind is the strongest correlating factor, but the fact remains that Alaska has extremely high rates of alcoholism, murder, child and other physical abuse, vehicular accidents, as well as other drug problems.
No one is going to call the cops if you're smoking a joint, even in public. They will think you're an asshole, and being an asshole is often a good way to be arrested. If you are drunk and weaving, and you have a bag in the glove compartment, you will probably be busted for both. If you're not going out of your way to bring the fact that you smoke pot into public view, everyone will be okay with that. That may not be your definition of legal, but it is certainly a definition of legal, and as much as you or I might wish it to be otherwise, it's pretty hard to argue with the vox populi.