Warren A. Koshofer

Partner
New York
+1 212-730-7700
wkoshofer@mrllp.com
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Warren A. Koshofer

Partner
“Clients don’t come to me for easy problems. They come when the stakes are high and the path forward demands experience, perspective, and a track record of wins.”

Warren Koshofer has spent his career at the intersection of law and business, advocating for clients in disputes where regulatory complexity and commercial risk collide. He counsels companies and individuals across the oil and gas, chemical, finance, real estate, luxury goods, and consumer products sectors.

Especially recognized for his work in environmental litigation, he handles matters involving Proposition 65, toxic torts, and environmental exposure. He also advises on mergers and acquisitions, delivering due diligence and risk assessments tied to environmental liabilities, insurance coverage, and indemnification. His work frequently touches on sustainability and ESG, particularly in the fashion and luxury goods industries.

He has represented clients in state, federal, and administrative courts across the country, litigating everything from contract and insurance disputes to intra-company conflicts and IP-related risks in commercial transactions. Many of his cases have helped shape how regulated businesses assess and respond to exposure.

With decades of litigation experience behind him, Warren brings a seasoned, measured perspective to each matter—helping clients stay focused, prepared, and in control through moments of legal and operational uncertainty. In addition to his practice, he leads the firm’s pro bono efforts, reinforcing his long-standing commitment to service and access to justice.

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Warren A. Koshofer

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Representative Matters

  • Business Litigation: Represented a cannabis-related business in wrestling control of its dispensary operations back from minority partners and obtaining favorable decisions on the client’s super-majority ownership rights.
  • CERCLA Defense: Successfully represented a metal plating operation in defense of CERCLA contribution claims brought by a neighboring property owner who, after aggressive litigation and receipt of counterclaims filed on the clients’ behalf, settled with the client for a “walk-away” dismissal of all claims.
  • Consumer Litigation (Insurance): Represented a large international insurance company sued by a public company policyholder contending that an insurance product was illusory, illegal and evidenced a pattern and practice justifying over $100M in damages. Devised a defense strategy that included filing suit against the policyholder for failing to pay certain policy premiums. Through litigation, secured a dismissal of the plaintiff’s lawsuit and recovered approximately $5M on client’s behalf.
  • Corporate Dispute: Successfully represented a managing member of an LLC by defeating all claims brought by other members of the LLC which alleged that the managing member misappropriated corporate opportunities and violated fiduciary duties. The client was completely vindicated in defense of all claims.
  • Due Diligence: Conducted due diligence on behalf of banks and other financial investors associated with contemplated new investments or loans, particularly with respect to environmental and litigation risks.
  • Environmental Defense: Successfully defended a client against action by the USEPA, which filed a complaint seeking millions of dollars in penalties for alleged regulatory violations. The USEPA alleged the client operated a plant that leaked a hazardous substance into the air before being shut down by USEPA. Choosing to push back against the proposed penalties versus a merit-based challenge, the dispute was favorably resolved for $5,000.
  • Insurance Coverage (Bad Faith Defense): Represented a prominent insurance company in the defense of an arbitration proceeding where the insured, under CGL insurance policies issued by the client, sought the return of several million dollars paid by the insured for, among other things, deductible obligations. After an aggressive defense, the case ultimately settled at mediation with the insured paying the insurer several million dollar.
  • Insurance Coverage (Policyholder): Represented product manufacturers in lawsuits with their liability insurers arising out of environmental and toxic tort claims. Overcame numerous challenges by the insurers, including claims that underlying layers of coverage were not exhausted and occurrences did not take place in particular policy years, to drive the insurers to the settlement table to fund environmental cleanup and defend toxic tort actions.
  • Proposition 65: Represented product manufacturers in California Proposition 65 cases relating to various products, including a bicycle manufacturer defending claims that the cables on its bicycles were subject to Prop 65 disclosures.
  • Securities Fraud Defense: Represented an investment banking firm in defense of a securities fraud case alleging hundreds of millions of dollars of losses stemming from an alleged pump and dump stock scheme.
  • Toxic Tort Defense: Represented a chemical manufacturer in the defense of more than 80 separate toxic tort cases filed by teachers and students at an elementary school which neighbored a plating operation site where the client’s chemicals were allegedly used. Led the defense to a very favorable settlement on client’s behalf.

Credentials

Bar & Court Admissions
  • California
  • New York
  • New Jersey
  • Pennsylvania
  • U.S. Court of Appeals for the Third Circuit
  • U.S. Court of Appeals for the Ninth Circuit
  • U.S. District Court for the Eastern, Central, and Southern Districts of California
  • U.S. District Court for the Southern, Eastern, and Northern Districts of New York
  • U.S. District Court for the District of New Jersey
Professional Affiliations
  • American Bar Association
  • California State Bar Association
  • New Jersey State Bar Association
  • New York State Bar Association
  • Environmental Law Institute
Community Involvement
  • Make a Wish Foundation
  • March of Dimes
  • United Way
  • Local Youth Football
Education
  • Rutgers University School of Law, J.D.
  • Rutgers University, B.A.
Recognition
  • AV® Preeminent Peer Review Rating, Martindale-Hubbell
  • New York “Super Lawyers”
  • California “Super Lawyers”
  • Who’s Who in Law, Marquis

Warren A. Koshofer

Partner
New York
+1 212-730-7700
wkoshofer@mrllp.com
“Clients don’t come to me for easy problems. They come when the stakes are high and the path forward demands experience, perspective, and a track record of wins.”
Overview

Warren Koshofer has spent his career at the intersection of law and business, advocating for clients in disputes where regulatory complexity and commercial risk collide. He counsels companies and individuals across the oil and gas, chemical, finance, real estate, luxury goods, and consumer products sectors.

Especially recognized for his work in environmental litigation, he handles matters involving Proposition 65, toxic torts, and environmental exposure. He also advises on mergers and acquisitions, delivering due diligence and risk assessments tied to environmental liabilities, insurance coverage, and indemnification. His work frequently touches on sustainability and ESG, particularly in the fashion and luxury goods industries.

He has represented clients in state, federal, and administrative courts across the country, litigating everything from contract and insurance disputes to intra-company conflicts and IP-related risks in commercial transactions. Many of his cases have helped shape how regulated businesses assess and respond to exposure.

With decades of litigation experience behind him, Warren brings a seasoned, measured perspective to each matter—helping clients stay focused, prepared, and in control through moments of legal and operational uncertainty. In addition to his practice, he leads the firm’s pro bono efforts, reinforcing his long-standing commitment to service and access to justice.

Practice Area

Consumer Products

Financial Services

Insurance

Commercial & Business Litigation

Environmental Law

Regulatory & Administrative Law

Representative Matters

  • Business Litigation: Represented a cannabis-related business in wrestling control of its dispensary operations back from minority partners and obtaining favorable decisions on the client’s super-majority ownership rights.
  • CERCLA Defense: Successfully represented a metal plating operation in defense of CERCLA contribution claims brought by a neighboring property owner who, after aggressive litigation and receipt of counterclaims filed on the clients’ behalf, settled with the client for a “walk-away” dismissal of all claims.
  • Consumer Litigation (Insurance): Represented a large international insurance company sued by a public company policyholder contending that an insurance product was illusory, illegal and evidenced a pattern and practice justifying over $100M in damages. Devised a defense strategy that included filing suit against the policyholder for failing to pay certain policy premiums. Through litigation, secured a dismissal of the plaintiff’s lawsuit and recovered approximately $5M on client’s behalf.
  • Corporate Dispute: Successfully represented a managing member of an LLC by defeating all claims brought by other members of the LLC which alleged that the managing member misappropriated corporate opportunities and violated fiduciary duties. The client was completely vindicated in defense of all claims.
  • Due Diligence: Conducted due diligence on behalf of banks and other financial investors associated with contemplated new investments or loans, particularly with respect to environmental and litigation risks.
  • Environmental Defense: Successfully defended a client against action by the USEPA, which filed a complaint seeking millions of dollars in penalties for alleged regulatory violations. The USEPA alleged the client operated a plant that leaked a hazardous substance into the air before being shut down by USEPA. Choosing to push back against the proposed penalties versus a merit-based challenge, the dispute was favorably resolved for $5,000.
  • Insurance Coverage (Bad Faith Defense): Represented a prominent insurance company in the defense of an arbitration proceeding where the insured, under CGL insurance policies issued by the client, sought the return of several million dollars paid by the insured for, among other things, deductible obligations. After an aggressive defense, the case ultimately settled at mediation with the insured paying the insurer several million dollar.
  • Insurance Coverage (Policyholder): Represented product manufacturers in lawsuits with their liability insurers arising out of environmental and toxic tort claims. Overcame numerous challenges by the insurers, including claims that underlying layers of coverage were not exhausted and occurrences did not take place in particular policy years, to drive the insurers to the settlement table to fund environmental cleanup and defend toxic tort actions.
  • Proposition 65: Represented product manufacturers in California Proposition 65 cases relating to various products, including a bicycle manufacturer defending claims that the cables on its bicycles were subject to Prop 65 disclosures.
  • Securities Fraud Defense: Represented an investment banking firm in defense of a securities fraud case alleging hundreds of millions of dollars of losses stemming from an alleged pump and dump stock scheme.
  • Toxic Tort Defense: Represented a chemical manufacturer in the defense of more than 80 separate toxic tort cases filed by teachers and students at an elementary school which neighbored a plating operation site where the client’s chemicals were allegedly used. Led the defense to a very favorable settlement on client’s behalf.

Credentials

Bar & Court Admissions
  • California
  • New York
  • New Jersey
  • Pennsylvania
  • U.S. Court of Appeals for the Third Circuit
  • U.S. Court of Appeals for the Ninth Circuit
  • U.S. District Court for the Eastern, Central, and Southern Districts of California
  • U.S. District Court for the Southern, Eastern, and Northern Districts of New York
  • U.S. District Court for the District of New Jersey
Professional Affiliations
  • American Bar Association
  • California State Bar Association
  • New Jersey State Bar Association
  • New York State Bar Association
  • Environmental Law Institute
Community Involvement
  • Make a Wish Foundation
  • March of Dimes
  • United Way
  • Local Youth Football
Education
  • Rutgers University School of Law, J.D.
  • Rutgers University, B.A.
Recognition
  • AV® Preeminent Peer Review Rating, Martindale-Hubbell
  • New York “Super Lawyers”
  • California “Super Lawyers”
  • Who’s Who in Law, Marquis

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