OK SB2078

Creates the "Oklahoma Diesel Engine Freedom Act" declaring federal diesel exhaust fluid (DEF) requirements null and void for vehicles operating solely within Oklahoma, based on 10th Amendment state sovereignty claims

Prohibits state agencies, political subdivisions, and state officers from enforcing any federal DEF mandates on vehicles operating within the state

Legalizes the manufacture, sale, and installation of diesel engines that do not require DEF, with such engines exempt from federal emissions standards if manufactured and sold exclusively within Oklahoma

Establishes civil fines for anyone enforcing federal DEF mandates: $500 for first offense, $1,000 for second offense, and $2,500 for third and subsequent offenses, with warnings for first-time violations and an administrative appeals process

Repeals existing Oklahoma law (47 O.S. 2021, Section 12-423) relating to emission control systems and includes an emergency clause for immediate effect upon passage