R.I. Gen. Laws § 6-36-6: Certain contracts unlawful.

A contract for the supplying of commodities or furnishing of services; or for the fixing of prices charged for the commodities or services; or for the giving or selling of a discount or rebate, on the condition, agreement, or understanding that one party shall not deal in the commodities or services of a competitor or competitors of the other party; is unlawful where the effect of the contract or the condition, agreement, or understanding may be to lessen competition or tend to create a monopoly in any line of commerce in any region of this state.