N.M. Stat. § 57-11-1
It shall be unlawful for any person who is engaged, either directly or indirectly, in the manufacture or distribution 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 such motor vehicles at retail in this state, on the condition or with an agreement or understanding, either express or implied, that such person so engaged in selling motor vehicles at retail shall in any manner finance the purchase or sale of any one or 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 number thereof only to a designated person or class of persons, when the effect of the condition, agreement or understanding so 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 such condition, agreement or understanding to finance the purchase or sale of motor vehicles or to purchase such conditional sales contracts, chattel mortgages or leases, and any such condition, agreement or understanding is hereby declared to be void and against the public policy of this state.
NMS § 57-11-1