Okla. Const. art. XIV, § 2
The Legislature shall have authority to classify loans and lenders, license and regulate lenders, define interest and fix maximum rates of interest; provided, however, in the absence of legislation fixing maximum rates of interest, all contracts for a greater rate of interest than ten percent (10%) per annum shall be deemed usurious; provided, further, that in contracts where no rate of interest is agreed upon, the rate shall not exceed six percent (6%) per annum.
Amended by Laws 1968, SJR 60, Section 1, State Question 454, Legislative Referendum 167, adopted at election held September 17, 1968.