There is actually a law in place that protects Bigfoot and other creatures that fall into a similiar category...
Undiscovered Species Protection Act
http://www.dumblaws.com/law/1917
Law Summary:
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The harassing of Bigfoot, Sasquatch or other undiscovered subspecies is a felony punishable by a fine and/or imprisonment.
Undiscovered Species Protection Act (Full Text of the Law)
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Whereas, there is evidence to indicate the possible existence of an undiscovered species a primate mammal variously described as Bigfoot, Sasquatch, an ape-like creature or a subspecies of Homo Sapiens.
Whereas, reported recent and past sightings, research by anthropologist, Primatologist, biologist, forensic experts, cryptozooligst, independent organizations, private individuals and the famous chimpanzee researcher Jane Goodall support this possibility.
Whereas, the absence of specific laws covering the slaying, taking, trapping or harassing of said specimens encourages laxity in the use of firearms and other deadly devices and poses a clear and present threat to the safety and well-being of persons living or traveling within the boundaries of the creatures habitat as well as to the creatures themselves.
Whereas, for the safety of all, the carrying or dispersing of firearms requires a sense of responsibility to all surrounding individuals and animals. It is the shooters full responsibility to correctly identify the species before the taking of aim and or the killing of a species, therefore ignorance will not absolve the shooter of said charges.
Whereas, be it resolved that any premeditated, willful and wanton slaying harassing or any malicious activities upon such creature shall be deemed a felony punishable by a fine not to exceed One hundred Thousand Dollars ($100.0000) and/or imprisonment, not to exceed ten (10) years.
Whereas, in the event of the slaying or capture of said creature any and all (moneys) proceeds and revenues shall be donated to a state college for future studies and or the protection of said creatures. The rights and physical possession to the said creature shall also be immediately donated to a state college, for further studies.
About This Law:
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From Wikipedia:
Read the full Wikipedia article on "Bigfoot in Popular Culture" here
http://en.wikipedia.org/wiki/Bigfoot_in_popular_culture
Skamania County, Washington passed a law regarding Bigfoot in 1969 declaring that "any willful, wanton slaying of such creatures shall be deemed a felony" subject to substantial fine and/or imprisonment. The fact that this legislation was passed on April 1 did not escape notice, but County Commissioner Conrad Lundy said that "this is not an April Fool's Day joke ... there is reason to believe such an animal exists." Hunter and Dahinden mention their own "speculation that Skamania County authorities had their ears tuned much more to the music of a publicity bandwagon than to any song of distress" for Bigfoot. Notwithstanding, the ordinance was amended in 1984 to preclude an insanity defense and to consider such a killing homicide if the creature was proven by the coroner to be humanoid.
In response to Al Magnussen from the Mt. Baker Chamber of Commerce, Whatcom County, Washington, an Agenda Bill was drafted (92-247) on 6/9/91, which unanimously passed a resolution declaring Whatcom County a Sasquatch Protection and Refuge Area.