They basically have the same law in Montana. If the bear poses an immediate threat to a person the person can shoot the bear. Not much of a problem of mass bear killings there.
Call the authorities? Depends on the situation. If there's time and a reasonable ability to wait for the authorities then fine call. But with turn around times being what they are, by the time the authorities get there, if you believe you'd be dead, or your house is going to be completely destroyed, then yeah might have to make the hard choice.