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Zachary C. Kleinsasser concentrates his practice on complex commercial litigation, with a particular emphasis on intellectual property matters, including trademark and copyright litigation, and defending news and entertainment organizations from news-gathering and publication-related claims, including defamation and invasion of privacy matters. He also has a wide-range of experience handling general business and employment disputes, including trade secret litigation, and representing developers, property owners, landlords and tenants in real estate matters involving commercial leases, purchase and sales agreements, construction agreements, land use, and property valuation. Zack has tried cases in state and federal courts and represented clients in arbitration hearings before the American Arbitration Association. Among Zack’s clients are companies and individuals in the fields of computer software, consumer products, entertainment, energy efficiency, health care, and insurance.


  • Trademark, copyright, and patent litigation
  • Trade secret litigation
  • Financial services litigation
  • Real estate and land use litigation
  • Commercial lease disputes
  • Media and First Amendment litigation
  • Internal corporate investigations



  • Affirmed judgment of dismissal in favor of company providing inmate calling services for lack of personal jurisdiction.  Paul McMann v. Global Tel*Link, __  F.3d __ (1st Cir. 2014).
  • After bench trial, obtained judgment for possession, unpaid rent, and attorney’s fees on behalf of commercial property owner (2014).
  • Represented financial services company in multimillion-dollar litigation with former consultant involving contract and Copyright Act claims. Obtained summary judgment dismissing all claims in their entirety. The Capability Group v. American Express Travel Related Services Co. Inc., 706 F. Supp. 2d 146 (D. Mass. 2010), aff’d, 658 F.3d 75 (1st Cir. 2011).
  • Defended international reinsurers in multimillion-dollar breach of contract and declaratory relief action. Obtained dismissal of all claims against reinsurers after jurisdictional discovery. OneBeacon American Insurance Co. v. Argonaut Insurance Co., et al., No. 09-5085-BLS1, slip op. (Mass. Super. Nov. 9, 2011).
  • Represented national newspaper and website publishing company as amicus curiae in matter involving the right to privacy in a civil recommitment proceeding. Kirk v. Commonwealth, 459 Mass. 67 (2011).
  • Represented telecommunications company in matter involving alleged breach of contract and violations of the Fair Credit Reporting Act (FCRA). After removing the case to federal court in Massachusetts based on the FCRA. The court dismissed the FCRA claim and two-state law causes of action. Leet v. Cellco Partnership, d/b/a Verizon Wireless, 480 F. Supp. 2d 422 (D. Mass. 2007). Court subsequently granted summary judgment on sole remaining cause of action. 2009 WL 613536 (D. Mass. March 11, 2009).
  • Represented publicly traded national retailer in Massachusetts federal court action involving misappropriation of trade secrets, breach of non-competition and non-solicitation agreements, and destruction of computer data files. Matter culminated in a two-week trial and a jury verdict on all claims. Casual Male Retail Group, Inc. v. Yarbrough, et al., 527 F. Supp. 2d 172 (D. Mass. 2007).
  • Represented financial services company in lawsuit challenging handling of checks deposited by controller as part of controller’s complex embezzlement scheme.
  • Represented national newspaper and website publishing company in defamation, public access and breach of contract actions.
  • Represented franchisee-dealers in resolution of multidistrict litigation against a multinational oil conglomerate involving claims for violations of the Petroleum Marketing Practices Act (PMPA) and the Massachusetts Uniform Commercial Code.
  • Represented international mattress and pillow manufacturer in patent infringement lawsuit against 17 bedding companies in the Western District of Virginia concerning the design and construction of "memory foam" mattresses.
  • Represented international mattress and pillow manufacturer in patent infringement lawsuit in the Western District of Virginia concerning the design and construction of "memory foam" pillows.
  • Represented financial services company in lease arbitration to determine fair market rent. Obtained unanimous award in client’s favor.
  • Represented special litigation committee of board of directors of a publicly traded telecommunications firm in investigation of historical stock option-granting practices in response to derivative litigation in federal and state court asserting claims for breach of fiduciary duty and violations of federal securities laws.
  • Represented private equity company in two multimillion-dollar matters in Massachusetts federal court involving breach of contract and breach of the covenant of good faith and fair dealing.
  • Represented prominent youth mentoring organization in Massachusetts federal court lawsuit involving trademark infringement under federal and state law. Obtained dismissal of all claims.
  • Conducted internal investigation of business practices at a major local and regional company.
  • Represented Massachusetts town in tax abatement proceedings before the Massachusetts Appellate Tax Board in action concerning a multitenant, multimillion-dollar commercial property.
  • Represented credit card company in matters involving check and payment fraud, including matters involving fictitious payees and defalcating employees and fiduciaries.

Sukcesy i wyróżnienia

  • Listed, Boston magazine, "Top Lawyers - Intellectual Property Rights," 2022
  • Listed, Super Lawyers magazine, Massachusetts Super Lawyers, "Rising Stars," 2013-2018
  • Member, Boston Bar Association


  • J.D., Boston College Law School
    • Clinical Program Director, Boston College Environmental Affairs Law Review
  • B.A., History, summa cum laude, Albion College
Posiadane uprawnienia
  • Massachusetts
  • U.S. Court of Appeals for the First Circuit
  • U.S. District Court for the District of Massachusetts
Znajomość języków
  • francuski