Each county board may make and establish written rules and regulations for the unconditional release of and may unconditionally release any prisoner who is not a citizen or national of the United States and who voluntarily consents to return or to be returned to their native land and who actually returns or is returned. The necessary expenses of the transportation of the prisoner and officers or attendants in charge of the prisoner may be paid by the county, upon order of the board of supervisors authorizing or ratifying the return of the prisoner at the expense of the county.