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Daniel Mensher


1201 Third Avenue, Suite 3200
Seattle, WA 98101 

P: 206.623.1900
F: 206.623.3384


Daniel Mensher translates thorough preparation into courtroom success. Dan practices in Keller Rohrback’s nationally-recognized Complex Litigation Group with a focus on environmental cases and representing government entities in important litigation. He collaborates with his colleagues and clients to identify problems and craft creative, long-lasting solutions.

Dan has litigated important environmental and consumer cases across the country in federal and state court. He presently represents the State of Oregon in its case against Monsanto seeking to hold the corporate giant responsible for natural resource damages related to its sale and marketing of PCBs. He is also part of the Keller Rohrback team representing more than 70 counties, cities, and tribes in the fight to hold drug manufacturers and other entities accountable for the opioid crisis.

Before joining the firm, Dan was an environmental law professor at Lewis & Clark Law School in Portland, Oregon, where he also litigated cases involving toxic waste, water pollution, and natural resource management. He has sat on governmental advisory boards and helped to draft key environmental regulations in place today. Dan uses his passion and experience to protect our environment and the people and communities that rely on clean air, water, and products.

Bar and Court Admissions

2007, Oregon

2008, U.S. District Court for the District of Oregon

2008, U.S. Court of Appeals for the Ninth Circuit

2010, U.S. District Court for the District of Columbia Circuit

2011, U.S. District Court for the Western District of Wisconsin

2014, Washington 

2014, U.S. District Court for the Eastern District of Washington

2014, U.S. District Court for the Western District of Washington


Wesleyan University – B.A., 1998, History

University of Wisconsin – M.S., 2002, Geography

Lewis & Clark Law School – J.D., cum laude, 2007; Environmental Law Certificate; Cornelius Honors Society; Articles Editor, Environmental Law Review

Professional and Civic Involvement

Oregon State Bar Association, Member

Washington State Bar Association, Member

Toxic Free Future, Board Member

Northwest Environmental Defense Center, Board Member, 2009-2014

Articles & Presentations

Speaker, Alliance of California Judges Symposium on the Economics of Consumer Protection, “Federalism and the Preemption of State Public Nuisance Actions,” November 2019

Speaker, Bridgeport Environmental Class Action Webinar, March 2016

Speaker, Harris Martin Porter Ranch Gas Leak Litigation Conference, “Testing of the Air Quality and Expert Witnesses for the Cases,” 19 January 2016

Daniel P. Mensher, With Friends Like These…: The Trouble With Auer Deference, 43 Envtl. Law Rev. 4 (2013)

Speaker, Oregon Water Law Conference, November 7, 2013 (Addressing issues in Water Quality Trading)

Speaker, Northwest Environmental Conference and Tradeshow, December 11, 2013 (The Precautionary Principle in Environmental Law)

Speaker, RainOps Conference, 2013, Spokane, WA, Longview, WA (Clean Water Act stormwater regulation)

Presenter, Oregon State Bar Environmental and Natural Resources Committee annual Continuing Legal Education Program, 2013 (salmon issues in Oregon and the Pacific Northwest)

Speaker, Oregon State Bar brown bag CLE debate with Oregon DOJ assistant attorney general about the Supreme Court case Decker v. NEDC, 2012

Daniel P. Mensher, Common Law On Ice: Using Federal Nuisance Law to Address Global Warming, 37 Envtl. Law Rev. 2 (2007)

Chris Rycewicz and Dan Mensher, Growing State Authority Under the Clean Water Act, 22 Nat. Resources & Env’t 2 (2007)

Recent Posts

Keller Rohrback Files Suits on Behalf of Skagit County, Mount Vernon, Sedro-Woolley, and Burlington Against Opioid Manufacturers 

King County and Keller Rohrback File Suit Against Opioid Manufacturers

Oregon Sues Monsanto, With the Help of Keller Rohrback, Over Toxic PCBs

More Cities and Governments File Suit Against Prescription Opioid Manufacturers

Keller Rohrback Files Suit Against Prescription Opioid Manufacturers

Court Grants Preliminary Approval of $142 Million Settlement in Wells Fargo Unauthorized Accounts Class Action

Court Grants Final Approval to 3.0-Liter Class Action Settlement & Bosch Class Action Settlement

Keller Rohrback: Plaintiffs in Wells Fargo Account Scandal Seek Court Approval for $142 Million Settlement

Keller Rohrback L.L.P.: Plaintiffs in Wells Fargo Account Scandal Seek Court Approval for $142 Million Settlement

Preliminary Approval of VW/Audi/Porsche 3-liter and Bosch Settlements in Volkswagen "Clean Diesel" Litigation

Bosch Agrees To $327.5 Million Settlement in VW Diesel Emissions Fraud Case

Settlement Agreement Filed for Volkswagen, Audi, Porsche 3.0-Liter

Important Info for Owners of TDI 3.0-Liter VWs/Audis/Porsches

Court Grants Final Approval 2.0-Liter Settlement

Volkswagen Litigation Update – 8/25/2016

Volkswagen Litigation Update – Preliminary Approval of VW Settlement Granted

Volkswagen Litigation Case Update

Volkswagen and Audi 2.0-Liter Emissions Settlement

Keller Rohrback L.L.P. Investigates High Levels of Lead in Children’s Cra-Z-Art Kits

VW Litigation Case Update

KR Investigating Claims Against Precision Castparts For Heavy Metal Pollution in Oregon

Keller Rohrback Investigates Claims Against Portland Glass Manufacturers For Arsenic and Cadmium Pollution

Keller Rohrback Files Class Action Lawsuit Against SoCalGas on Behalf of Porter Ranch Residents

Keller Rohrback Investigates Claims of Diesel Porsche Cayenne Consumers

JPML Sends VW Lawsuits to San Francisco

Class Action Lawsuit Filed on Behalf of Those Affected by Refugio Oil Spill

Village of Rockton Fights Abandoned Sonoco Paper Mill Contamination

Keller Rohrback Files Suit on Behalf of Porsche, Audi, and VW Consumers

Keller Rohrback Warns Consumers About VW Goodwill Package

Keller Rohrback Expands Nationwide Class Action Lawsuit Against VW

KR Launches Investigation After EPA Adds Audi & Porsche to VW Clean Air Act Violation

Keller Rohrback Files Nationwide Class Action Lawsuit Against Volkswagen

VW Emissions Scandal

Volkswagen's Alleged Violation of Clean Air Standards

Volkswagen Investigated by EPA Over Clean Air Standards

Volkswagen Violates Clean Air Act

Volkswagen Class Action Complaint Expands To Include Affected Porsche and Audi Vehicles

KR Asks Federal Judge to Prohibit VW and Audi From Making Misleading Statements to Drivers

Keller Rohrback Investigates Oil Company Price Fixing

Keller Rohrback Asks Judge To Stop Misleading Communications

Volkswagen News From Around The Web

Volkswagen Help Center - Useful Links

KR attorney Dan Mensher discusses environmental impact of VW Dieselgate

Meet the Keller Rohrback Volkswagen Team

Keller Rohrback Advocates for Volkswagen Diesel Consumers Nationwide in Class Action

Nationwide Class Action Complaint Filed Against VW

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