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• January 28, 2019 - CADA files a complaint against the Colorado Department of Public Health and Environment, alleging violations of the Colorado Administrative Procedures Act, Air Pollution Prevention and Control  Act, and Colorado Constitution.                                                                                        

• February 21, 2019 - The Office of the Attorney General files a motion to dismiss against CADA for lack of standing.                                                                                              

• March 15, 2019 - The Environmental Caucus submits a motion to intervene in the case, defending the making of Regulation 20.                                                                                                         

• July 8, 2019 - The District Court for the City and County of Denver issues an order granting the State's motion to dismiss.                                                                                               

• July 26, 2019 - CADA files a Notice of Appeal to the Colorado Court of Appeals, seeking to vacate and remand the lower court's order.

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• December 20, 2019 - Case is held in abeyance until California v. EPA, No. 18-1114 (DC Cir 2019) is resolved.  This case impacts the revocation of California's waiver under the Clean Air Act.

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• August 26, 2020 - State cases continue to be held in abeyance as the DC Circuit Court completes its backlog of cases due to the Coronavirus shut down.