Pashman Stein Walder Hayden P.C. Named New Jersey Law Journal’s Law Firm of the Year 2023*

Sean Mack, Pashman Stein Walder Hayden P.C. Photo

Sean Mack

Co-Chair, Litigation and Chair, Cannabis & Hemp Law; Executive Committee Member


Sean Mack is the co-chair of the firm's Litigation practice and chair of the firm’s Cannabis and Hemp practice. He also serves as a member of the firm's Executive Committee. Clients turn to Sean for his steadfast guidance, sincere interest in the success of their businesses, and extensive knowledge of New Jersey’s and New York’s regulations and case law in the cannabis and hemp industries, for both adult-use recreational marijuana and medical marijuana.

Business Litigation

Sean’s business litigation practice focuses on complex disputes involving unfair business competition. He regularly represents businesses, business owners and senior executives in lawsuits involving theft of corporate opportunities, theft of trade secrets, breaches of non-competition agreements, breaches of confidentiality and non-disclosure agreements, and other unfair business practices. Clients often retain Sean when a joint business venture has gone awry or when they believe it is time to divorce their business partners. Many of his cases arise from complicated contractual and licensing disputes. He also has represented clients in trademark and trade dress infringement cases and in counterfeiting cases. With his strong business acumen, he is often brought in to advise firm clients on bankruptcy and insolvency-related issues, and has represented creditors and debtors in bankruptcy proceedings. He also has represented several firm clients in contested probate proceedings.

Appellate Advocacy

Sean is an experienced appellate advocate, having presented appeals in many federal and state courts. Sean often leads teams of Pashman Stein attorneys to prosecute appeals of complex matters that were lost at the trial level by other law firms. 

Sean began his legal career with Debevoise & Plimpton LLP, where he practiced commercial litigation for many years before joining Pashman Stein in 2005.


With significant experience counseling business owners in complex disputes, Sean brings a unique set of skills to businesses interested in cannabis and hemp. Sean advises Hemp-CBD companies on state and federal laws affecting their advertising and businesses. He also works in tandem with Pashman Stein’s attorneys to offer clients counsel in the interplay between cannabis/hemp laws and corporate, employment, intellectual property, health care and real estate laws.

Recognized on the InsiderNJ “Insider 100: Cannabis Power List” in 2022, 2021 and 2019 as an influential voice in the cannabis debate, Sean has been active in cannabis reform since 2015, when he led a team of the firm’s attorneys to analyze existing cannabis laws and regulations to prepare proposed legislation for New Jersey United for Marijuana Reform (NJUMR). NJUMR then presented the firm’s proposal to a state senator for incorporation into an early draft of the bill to legalize adult use marijuana in New Jersey.

Sean advises businesses interested in applying for cannabis or hemp licenses in New York and New Jersey, and he has represented clients in appeals of the 2018 and 2019 rounds of New Jersey medical marijuana license applications.  Sean has assisted more than two dozen companies to work through the complicated adult use licensing process in New Jersey and New York. 

He also advises companies and individuals on the specific protections afforded to medical marijuana patients under the Jake Honig Act in employment, the receipt of medical services, and real estate.  

In Sean's Words:

"As chair of the firm’s Cannabis and Hemp practice, I have a rare opportunity to assist entrepreneurs and business owners as they form and operate new ventures in New York and New Jersey’s quickly growing recreational adult-use industry. The laws and regulations are evolving and are often in conflict at the state and federal level, presenting challenges to an already competitive landscape. The protections afforded to medical marijuana patients under state law, in employment, medical services and real estate, also present significant business issues for clients and considerable review in our courts. On behalf of our clients in the cannabis and hemp industries, I collaborate with my Pashman Stein colleagues to provide a full spectrum of cannabis-related legal and business counsel." 


Representative Matters

Our firm is proud of the results it has achieved for clients, some of which are noted here.  Of course, each legal matter is unique on many levels, and past successes are not a guarantee of results in any other pending or future matters.

  • Pashman Stein Walder Hayden worked with New Jersey United for Marijuana Reform and ACLU-NJ in 2015 to draft the legislation that was introduced by Senator Scutari in 2017. Senator Scutari’s bill ultimately was passed into law in 2021.
  • Represented appellants in appeals of the 2018 and 2019 New Jersey requests for applications for licenses for medical cannabis alternative treatment centers.
  • Assisted twenty clients during 2022 to obtain conditional licenses for cultivation, manufacturing and adult use dispensaries in New Jersey.
  • Represented a leading heart valve manufacturer in a patent licensing dispute involving rights to a minimally invasive method for repairing and replacing aortic heart valves (transcatheter aortic valve replacement therapy).The dispute focused on whether only a particular patent or an entire family of patents to the revolutionary heart valve device and procedure had been licensed. Following an evidentiary hearing on our application for summary judgment, the matter was resolved through a confidential settlement.
  • Successfully obtained the dismissal of all federal Lanham Act claims brought by a lighting company against its former contract manufacturer in a suit alleging that the manufacturer stole trade secrets and was improperly competing with the lighting company in breach of a confidentiality agreement. Then successfully obtained the dismissal of a follow-on lawsuit in state court on the basis of choice of law and personal jurisdiction defects. We then successfully pursued insurance coverage for all of the defense costs and expenses in federal court and on appeal before the Second Circuit Court of Appeals.
  • Successfully defended a lawsuit brought by a sibling in a family-owned business, who after 30 years of having no involvement with the business, demanded his share of the business and its profits. Despite the existence of an old stock ledger supporting the claim, the plaintiff was awarded zero dollars on his claims.
  • Successfully defended national sales representative against claims of breach of a non-competition and non-solicitation agreement after he joined a direct competitor.
  • Successfully obtained a preliminary injunction prohibiting a former senior executive from competing against his former employer anywhere in the state of New Jersey and successfully prosecuted an order for sanctions when the former employee violated the injunction.
  • Represented major investment bank as investment advisor in connection with several bankruptcy matters
  • Represented numerous firm clients as creditors in contested adversary proceedings and in defense of preference claims in bankruptcy matters.
  • Represented the following in each of their Chapter 11 cases: a casino, a major steel manufacturer, and a global building and construction materials company.
  • Successfully obtained a temporary restraining order compelling a medical service provider to continue providing needed medical services, which had been denied solely because the patient obtained his medical cannabis card from the State of New Jersey.
  • Successfully pursued patent, trademark and trade dress lawsuits on behalf of a leading manufacturer of industrial torque wrenches to stop several companies from selling knock-offs of our client’s wrenches.
  • Successfully represented owner of a condo against charges from his condo association that his use of medical marijuana in his condo violated condo association rules.
  • Successfully resolved a lawsuit against a senior executive of major pharmaceutical company in a case involving claims of breach of a non-competition agreement when she joined another major pharmaceutical company.

Reported Decisions

  • National Lighting Company, Inc. v. Bridge Metal Industries, LLC, 601 F.Supp.2d 556 (S.D.N.Y. 2009)
  • Strahan v. Strahan, 402 N.J.Super. 298 (App. Div. 2008)
  • Arnold v. Arnold, 2007 WL 1146627 (N.J. App. Div. 2007)
  • In re XO COMMUNICATIONS, INC., 323 B.R. 330 (Bankr. S.D.N.Y. 2005)
  • Hawa Abdi Jama v. Esmor, 343 F.Supp.2d 338 (D.N.J. 2004) and 334 F. Supp 2d 662 (D.N.J. 2004)
  • Burns v. Anderson, 123 Fed.Appx. 543 (4th Cir. 2004)
  • In re RSL Primecall, Inc., 2003 WL 22989669 (Bankr. S.D.N.Y. 2003)


Honors & Recognitions

Selected for inclusion in the list of:

  • InsiderNJ, “Insider 100: Cannabis Power List,” 2022, 2021 & 2019
  • Best Lawyers, Commercial Litigation, 2013-2024
  • New Jersey Super Lawyers, 2016-2024
  • New Jersey Super Lawyers, Rising Star, 2010-2013

The Super Lawyers list is issued by Thomson Reuters. A description of the selection methodology can be found at

The Rising Stars list is issued by Thomson Reuters. A description of the selection methodology can be found at

The Best Lawyers list is issued by Woodward/White, Inc. A description of the selection methodology can be found at

The Insider 100: Cannabis Power List is issued by Insider NJ. A description of the selection methodology can be found at

No aspect of this advertisement has been approved by the Supreme Court of New Jersey.

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Community & Professional

  • Member, New Jersey Bar Association
  • Member, Bergen County Bar Association
  • Former Member, District II-B Ethics Committee

Bar Admissions

  • New Jersey
  • New York

Court Admissions

  • U.S. District Court, District of New Jersey
  • U.S. District Court, Southern District of New York
  • U.S. District Court, Eastern District of New York
  • U.S. Court of Appeals, Second Circuit
  • U.S. Court of Appeals, Fourth Circuit
  • U.S. Court of Appeals, Sixth Circuit


B.A., College of the Holy Cross, 1995, cum laude

J.D., Rutgers University School of Law, 1999, with highest honors, Order of the Coif

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