On the regulatory side, he has helped companies and trade associations prepare comments on scores of proposed rules including revisions to the ozone and particulate matter NAAQS, several rounds of PSD/NSR regulations (e.g., the WEPCO rule in 1992, the NSR Reform rule in 2002, the equipment replacement rule in 2003, and the Duke hourly rate rule in 2006), numerous MACT standards (e.g., the boiler, commercial and industrial solid waste incinerator, aerospace, coil coating, site remediation, medical waste incinerator, off-site waste and recovery (OSWRO), wool fiberglass, hazardous waste combustors, lime manufacturing, and MON rules), the credible evidence rule, federal and state Title V rules, and state and local rules (e.g., CARB rules for off-road diesel engines and large spark-ignition engines). He has litigated many of these rules in the D.C. Circuit and elsewhere either as an industry petitioner or as an intervenor in suits brought by environmental groups. Most of these cases have resulted in favorable settlements (e.g., litigation relating to the OSWRO residual risk and technology (RTR) rule,  the organic liquids distribution MACT, the aerospace MACT), while others have resulted in published opinions. See, e.g. U.S. Sugar Corp. v. EPA, 830 F.3d 579 (D.C. Cir. 2016), Sierra Club v. EPA, 167 F.3d 658 (D.C. Cir. 1999); Cement Kiln Recycling Coalition v. EPA, 255 F.3d 855 (D.C. Cir. 2001).

Once the rules are in place, he counsels a wide range of companies on compliance. His clients include petroleum refineries, chemical manufacturers, cement and glass manufacturers, pharmaceutical producers, consumer products manufacturers, waste management entities such as landfills and waste to energy facilities, can manufacturers, wastewater treatment plants, real estate developers, communications companies, and trade associations representing numerous industries such as lime manufacturers, the airlines, road and home building, and chemical companies. Day to day counseling issues include compliance with the complicated preconstruction permitting requirements of the federal and state PSD/NSR programs; compliance with the plethora of NESHAP and NSPS standards; responses to over fifty Section 114 requests for a diverse group of companies; and counseling on a wide range of Title V questions, including the application for, amendment and appeal of, and certification of compliance with, these permits that are often hundreds of pages long.

Finally, he defends companies accused of violating clean air regulations in suits brought by EPA, the Department of Justice, state environmental authorities, and citizen groups.