In Québec, it is called a "positive obligation"
under either the Civil code or the Charter of Rights (I have sent my little lawyer friend off to find out.) There is, however, a distinction to be made between whether or not the house is burning down or burning down with people inside. If the former there might be some grounds for bringing a suit on the grounds of negligence but apparently it is difficult to convict a person based solely on "acts of ommission". But, if the latter and you didn't call 911 and the person dies then you can be sued for having not fulfilled a civic responsibility. This was enforced a few years back when a driver neglected to provide any kind of assistance for persons stranded on the side of the road and they subsequently died of exposure. Equally important is the provision that says if you do come to the aid of a person and something bad, but unintentional, happens in the process you, personally, are immune from further suit. This is refered to as the "Good Samaritan" clause; something that apparently the American legal system overlooked much to the delight of its practitioners.