Ohio's SIP was submitted to the EPA. Approval of a portion of the plan was denied because it was not adequate to ensure the attainment and maintenance of the primary standard for photochemical oxidants in the Cincinnati area. The EPA supplemented the Ohio plan with a provision requiring a vehicle inspection and registration procedure for the Cincinnati area. Cincinnati set up the requisite inspection facilities but refused to withhold registration from those vehicles failing the inspection. The EPA sought an injunction ordering Ohio to implement "as written" the inspection and registration procedure described in the plan. Was the injunction granted? Explain.