This bill aims to significantly alter federal emissions regulations for motor vehicles, particularly by targeting a specific Environmental Protection Agency (EPA) rule. It explicitly prohibits the EPA from implementing or enforcing its "Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles—Phase 3" rule, which was published in April 2024. Beyond this immediate prohibition, the legislation amends the Clean Air Act to impose new, broader restrictions on future tailpipe emissions regulations. These amendments ensure that regulations cannot mandate the use of any specific technology or limit the availability of new motor vehicles based on their engine type. The bill further mandates that the EPA Administrator revise existing regulations within two years to conform to these new statutory requirements, aiming to prevent federal regulations from dictating vehicle technology or market access.