"U.S. Trial Firm of the Year" – 3 Consecutive Years (Benchmark; Law360)
Arianna Demas Portrait






  • Hon. Ronnie Abrams, U.S. District for the Southern District of New York


  • New York

Arianna Demas focuses her practice on high-stakes business disputes, complex litigation, and white collar investigations.

Prior to joining Hueston Hennigan, Ms. Demas was a William J. Brennan First Amendment Fellow for the American Civil Liberties Union. While in law school, Ms. Demas worked as an intern for the Knight First Amendment Institute at Columbia University and as an intern for the Hon. Sandra L. Townes for the United States District Court for the Eastern District of New York. She also served as the executive editor for the Michigan Law Review.


Representing Kelly Toys, maker of the top-selling toy in the US for 2023 “Squishmallows,” in a copyright infringement lawsuit against Build-A-Bear Workshop for its copycat Skoosherz product. (See “Squishmallows has launched a legal fight against Build-A-Bear,” BBC; “Squishmallows Battle Skoosherz In Plushie IP Suits,” Law360).

Defending Amazon.com and Twitch against multiple lawsuits arising out of the tragic May 2022 mass shooting at a grocery store in Buffalo, NY. Plaintiffs claim that Amazon.com, Twitch, and other social media services incentivized the shooter to commit his horrific crimes by, among other things, providing him with the ability to livestream his attack. Plaintiffs’ claims, which include product liability, negligence, and other torts, raise significant issues relating to the First Amendment and the scope of immunity for social media services under Section 230 of the Communications Decency Act.

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Secured a complete victory for McDonald’s USA against Byron Allen in a $100 million fraud suit over ad spend on black-owned media, through a motion brought under California’s “anti-SLAPP” statute. (See “McDonald’s Gets Anti-SLAPP Win In Allen’s $100M Fraud Suit,” Law360; Byron Allen Loses $100M Fraud Lawsuit Against McDonald’s Over Ad Spend on Black-Owned Media,” The Hollywood Reporter).

Represented Monster Energy in various federal lawsuits concerning marketing and advertising.

Represent former Board of Directors in a federal securities lawsuit in S.D.N.Y. regarding statements made in relation to their company’s public offering.

Successfully represented a high school student in U.S. Supreme Court case regarding students’ First Amendment speech rights, prevailing in an 8-1 decision.

Successfully represented a high-profile former Trump counsel in federal habeas corpus case in S.D.N.Y. after the government revoked his release from prison for his efforts to publish an anti-Trump book in violation of his First Amendment rights.

Represented journalists in a lawsuit against the federal government for its improper detention and interrogation of them at the border in violation of their First Amendment rights.

Lead attorney in federal lawsuit against the FBI in relation to its “Electronic Device Analysis Unit,” regarding its ability to gain access to encrypted devices.