The final greenhouse gas (GHG) Tailoring Rule includes a step- by-step implementation strategy for issuing Federally-enforceable permits to the largest, most environmentally significant sources beginning January 2, 2011. In this action, EPA is finalizing its proposed rulemaking to narrow EPA's previous approval of State title V operating permit programs that apply (or may apply) to GHG-emitting sources. Specifically, in this final rule, EPA is narrowing its previous approval of certain State permitting thresholds for GHG emissions so that only sources that equal or exceed the GHG thresholds established in the final Tailoring Rule would be covered as major sources by the Federally-approved programs in the affected States. By raising the GHG thresholds that apply title V permitting to major sources in the affected States, this final rule will reduce the number of sources that will be issued Federally-enforceable title V permits and thereby significantly reduce permitting burdens for permitting agencies and sources alike in those States.