Volunteers under this part shall, upon enrollment, take the oath of office as prescribed for persons appointed to any office of honor or profit by section
3331 of title
5, and shall swear (or affirm) that the volunteer does not advocate the overthrow of the constitutional form of government of the United States and that the volunteer is not a member of an organization that advocates the overthrow of the constitutional form of government of the United States, knowing that such organization so advocates, except that persons legally residing within a State but who are not citizens or nationals of the United States, may serve under this part without taking or subscribing to such oath, if the Director determines that the service of such persons will further the interests of the United States. Such persons shall take such alternative oath or affirmation as the Director shall deem appropriate.