Mont. Code Ann. § 28-10-606
28-10-606 Extent to which principal bound by acts under ostensible authority
28-10-606 . Extent to which principal bound by acts under ostensible authority. A principal is bound by acts of the principal's agent under a merely ostensible authority to those persons only who have in good faith and without ordinary negligence incurred a liability or parted with value upon the faith of the authority.