Idaho Code § 9-503: Transfers of real property to be in writing.

No estate or interest in real property, other than for leases for a term not exceeding one (1) year, nor any trust or power over or concerning it, or in any manner relating thereto, can be created, granted, assigned, surrendered, or declared, otherwise than by operation of law, or a conveyance or other instrument in writing, subscribed by the party creating, granting, assigning, surrendering or declaring the same, or by his lawful agent thereunto authorized by writing.