§ 312. Exclusiveness of remedy. Compensation as provided in this article shall be the exclusive remedy of a civil defense volunteer or his or her spouse, dependents, executor or administrator, for injury, disease or death arising in the course of civil defense volunteer service, as against the state or any political subdivision of the state or civil defense agency or any person or other agency acting under governmental authoritiy in furtherance of civil defense activities, with or without negligence, except only as otherwise provided by law. A member of a civil defense agency of the federal government or of another state or of the Dominion of Canada or a province thereof, who may perform services within this state, whether pursuant to a mutual aid compact or otherwise, shall not be entitled to compensation under the provisions of this article.