Is it legal to overload a plane in Alaska?
Under some conditions, FAR §91.323 allows for a 15% increase (up to 12,500 lbs) in max gross weight in Alaska:


  (a) Notwithstanding any other provision of the Federal Aviation Regulations, the Administrator will approve, as provided in this section, an increase in the maximum certificated weight of an airplane type certificated under Aeronautics Bulletin No. 7–A of the U.S. Department of Commerce dated January 1, 1931, as amended, or under § 91.325 14 CFR Ch. I (1–1–05 Edition) the normal category of part 4a of the former Civil Air Regulations (14 CFR part 4a, 1964 ed.) if that airplane is operated in the State of Alaska by—
  
  
  A certificate holder conducting operations under part 121 or part 135 of this chapter; or
  The U.S. Department of Interior in conducting its game and fish law enforcement activities or its management, fire detection, and fire suppression activities concerning public lands.
  
  
  (b) The maximum certificated weight approved under this section may not exceed—
  
  
  12,500 pounds;
  115 percent of the maximum weight listed in the FAA aircraft specifications;
  The weight at which the airplane meets the positive maneuvering load factor requirement for the normal category specified in § 23.337 of this chapter; or
  The weight at which the airplane meets the climb performance requirements under which it was type certificated.
  
  
  (c) In determining the maximum certificated weight, the Administrator considers the structural soundness of the airplane and the terrain to be traversed.
  
  (d) The maximum certificated weight determined under this section is added to the airplane's operation limitations and is identified as the maximum weight authorized for operations within the State of Alaska.




One possible reason for this is that Alaska Statute Section 02.35.110 requires aircraft operating to/from and within Alaska to carry additional emergency and survival equipment:


  (a) An airman may not make a flight inside the state with an aircraft unless emergency equipment is carried as follows:
  
  
  the following minimum equipment must be carried during the summer months:
  
  
  rations for each occupant sufficient to sustain life for one week;
  one axe or hatchet;
  one first aid kit;
  an assortment of tackle such as hooks, flies, lines, and sinkers;
  one knife;
  fire starter;
  one mosquito headnet for each occupant;
  two small signaling devices such as colored smoke bombs, railroad fuses, or Very pistol shells, in sealed metal containers.
  
  in addition to the equipment required under (1) of this subsection, the following must be carried as minimum equipment from October 15 to April 1 of each year:
  
  
  one pair of snowshoes;
  one sleeping bag;
  one wool blanket or equivalent for each occupant over four.
  
  
  
  (b) However, operators of multi-engine aircraft licensed to carry more than 15 passengers need carry only the food, mosquito nets, and signalling equipment at all times other than the period from October 15 to April 1 of each year, when two sleeping bags, and one blanket for every two passengers shall also be carried. All of the above requirements as to emergency rations and equipment are considered to be minimum requirements which are to remain in full force and effect, except as further safety measures may be from time to time imposed by the department.