Subchapter IV. Natural Gas Curtailment Policies 15 U.S. Code §3391. Natural gas for essential agricultural uses 15 U.S. Code §3391a. "Essential agricultural use" defined 15 U.S. Code §3392. Natural gas for essential industrial process and feedstock uses 15 U.S. Code §3393. Establishment and implementation of priorities 15 U.S. Code §3394. Limitation on revoking or amending certain pre-1969 certificates of public convenience and necessity