The infamous General Order No. 1 is the DoD rule that prohibits US personnel serving in Afghanistan from indulging in certain vices which are both endemic to military personnel and haram under Islamic law. Chief among these are alcohol, pornography and gambling.
Needless to say, the ban on alcohol is not popular, and not all countries in ISAF enforce it. Some European nations have their own version of the rule, which is equally unpopular. The Norwegians in particular have instituted a ban on alcohol among their troops, and importantly on any troops serving under Norwegian command. The fragmented nature of the ISAF command structure means that lots of troops from smaller countries serve under the regional command of the larger contributors.
Hence the problem. The Finns have a small detachment up north under Norwegian command who are now subject to the alcohol ban. Anyone who know Finns knows that denying them their daily ration of booze is a sure-fire way to stimulate dissent.* No different in this case. The Finns are very attached to their time-honored "Two Can Rule." The story is here (if you read Finnish, which I don't).
*Full disclosure: my mother's family are Finns, so I'm passingly familiar with the native fondness for alcohol. Some might even say that the Finnish side of my heritage is overrepresented in my personal behaviour.
Personally, my experience is that the Finns are a lot more likely to fight if you give them a little booze. Otherwise they just lapse into their natural depressive state.
h/t to Jari.