A trust is not valid unless evidenced by one of the following methods: (1) by a written instrument signed by the trustee or by the trustee's agent if authorized in writing to do so; (2) by a written instrument signed by the settlor or by the settlor's agent if authorized in writing to do so; or (3) by operation of law.
Statute Of Frauds
Mont. Code Ann. § 72-38-407, under Creation, Validity, Modification, and Termination of Trust.
Mont. Code Ann. § 72-38-407