The Oklahoma Diesel Engine Freedom Act establishes the state's authority to regulate emissions standards for vehicles operating solely within its borders, asserting that federal mandates requiring the use of diesel exhaust fluid in diesel engines are unconstitutional. The Act nullifies any federal regulations or executive orders related to this requirement and prohibits state agencies from enforcing such mandates. It emphasizes the state's rights under the 10th Amendment of the U.S. Constitution, declaring that the manufacture, sale, and installation of diesel engines that do not require diesel exhaust fluid are lawful within Oklahoma.

Additionally, the Act includes provisions for penalties against any state agency or individual attempting to enforce federal diesel exhaust fluid mandates, with fines up to $5,000 per violation and potential suspension or termination of employment for state officers. The bill also repeals 47 O.S. 2021, Section 12-423, which pertains to emission control systems, and declares an emergency for its immediate implementation.