Ensure means to make sure, certain, or safe.
Example of a Statute in California using the word ensure.
Cal Health & Saf Code § 39607.5: Method for valuation of credits for emission reductions
(a) The state board shall develop, and adopt in a public hearing, a methodology for use by districts to calculate the value of credits issued for emission reductions from stationary, mobile, indirect, and areawide sources, including those issued under market-based incentive programs, when those credits are used interchangeably.
(b) In developing the methodology, the state board shall do all of the following:
(1) Ensure that the methodology results in the maintenance and improvement of air quality consistent with this division.
(2) Allow those credits to be used in a market-based incentive program adopted pursuant to Section 39616 that requires annual reductions in emissions through declining annual allocations, and allow the use of all of those credits, including those from a market-based incentive program, to meet other stationary or mobile source requirements that do not expressly prohibit that use.
In the above context ensure means to make sure. The state board while developing the methodology should make sure that the methodology results in the maintenance and improvement of air quality that is consistent with the division.