Idaho Code § 49-2401
It shall be unlawful for any person who is engaged, either directly or indirectly, in the manufacture or wholesale distribution only of motor vehicles to sell or enter into a contract to sell motor vehicles, whether patented or unpatented, to any person who is engaged or intends to engage in the business of selling those motor vehicles at retail in this state, on the condition or with an agreement or understanding, either express or implied, that a person engaged in selling motor vehicles at retail shall in any manner finance the purchase or sale of any one or a number of motor vehicles only with or through a designated person or class of persons, or shall sell and assign the conditional sales contracts, chattel mortgages or leases arising from the sale of motor vehicles or any one or a number of motor vehicles only to a designated person or class of persons, when the effect of the condition, agreement or understanding entered into may be to lessen or eliminate competition, or create or tend to create a monopoly in the person or class of persons who are designated by virtue of that condition, agreement, or understanding to finance the purchase or sale of motor vehicles, or to purchase conditional sales contracts, chattel mortgages or leases.
Any such condition, agreement or understanding is hereby declared to be void and against the public policy of this state.
Idaho Code § 49-2401