Daniel J. Hay

Daniel frequently represents clients in litigation against government agencies and in commercial disputes in highly regulated industries. Daniel’s recent and ongoing representations include:

• Ford v. TD Ameritrade, Inc., 115 F.4th 854 (8th Cir. 2024): Successfully represented broker-dealer in overturning class certification order in a securities fraud class action in a suit arising out of the intersection between the duty of best execution, order routing and high-frequency trading. The Sidley team was named a runner up for Am Law’s “Litigator of the Week” for this victory.
• Clear Channel Outdoor v. City of New Rochelle (S.D.N.Y. 2024): Prevailed on summary judgment on behalf of a leading advertising company in complex Takings, First Amendment, preemption, and breach of contract challenge to a local government ordinance.
• FTC v. Microsoft Corp., 681 F. Supp. 3d 1069 (N.D. Cal. 2023), 136 F.4th 954 (9th Cir. 2025): Part of a trial and appellate team that successfully represented Microsoft against an antitrust challenge to its $68.7 billion acquisition of Activision, which was described by the trial court as “one of the largest, if not the largest, tech industry mergers.”
• NCFA v. Blinken, 4 F. 4th 106 (D.C. Cir. 2021): Successfully argued and briefed a challenge to agency guidance documents, which the D.C. Circuit unanimously vacated on the grounds that the guidance imposed new legislative rules without notice and comment. Daniel also persuaded the D.C. Circuit to reverse the district court’s ruling that our client lacked associational standing.
• NYSDEC v. FERC, 991 F.3d 439 (2d Cir. 2021) and National Fuel Gas Supply Corp. v. NYSDEC, 761 F. App’x 68 (2d Cir. 2019): Successfully represented an energy company in a pair of petitions for review concerning our client’s authority to construct a federally approved natural gas pipeline. Law360 awarded the Sidley team its “Legal Lion of the Week” title for this victory.
• United States of America v. AT&T, 916 F.3d 1029 (D.C. Cir. 2019): Successfully represented AT&T in the government’s appeal of the district court decision allowing AT&T to merge with Time Warner. The Wall Street Journal described this decision as “cement[ing] one of the biggest losses for the Justice Department’s antitrust division in a generation.”
• Mallory v. Norfolk Southern Railway Co., 600 U.S. 122 (2023): Represented respondent in Supreme Court merits case regarding the validity of statutes mandating consent to general personal jurisdiction.
• Biden v. Nebraska, 143 S. Ct. 2355 (2023): Amicus counsel to a coalition of former government officials, including former attorneys general and OMB directors, in a high-profile challenge to the executive action forgiving student debt.
• Murphy v. NCAA, 138 S. Ct. 1461 (2018): Authored an amicus brief on behalf the American Gaming Association (AGA), arguing that the Professional and Amateur Sports Protection Act, a federal law that effectively prohibited sports betting in most states, violated the Tenth Amendment and enabled a massive, unregulated black market. In a 7-2 decision citing Sidley’s brief, the Supreme Court agreed and held states were allowed to decide for themselves whether to legalize sports betting.
• IGT PLC v. Garland, 628 F. Supp. 3d 393 (D.R.I. 2022) and New Hampshire Lottery Commission v. Rosen, 986 F.3d 38 (1st Cir. 2021): Represented International Game Technology (IGT), one of the world’s largest lottery and casino gaming companies, as amicus and successfully challenged the Department of Justice’s reinterpretation of the Wire Act to reach non-sports betting. The U.S. Court of Appeals for the First Circuit affirmed a declaratory judgment in favor of another lottery company, but vacated farther-reaching relief that would have provided IGT freedom to operate. IGT then sued in the U.S. District Court for the District of Rhode Island, seeking a declaratory judgment that its nationwide non-sports betting operations were not subject to the Act. The Court granted summary judgment in favor of IGT, rejecting the government’s argument that IGT lacked standing because its risk of prosecution was not sufficiently imminent.
• Representing a leading dietary supplement labeler in multiple putative class actions asserting false and deceptive advertising practices.
• Representing a major global technology company on charges of racketeering, trade secret theft, bank fraud, and other alleged offenses.
• Represented a Fortune 500 financial services/FinTech company in a deceptive advertising and unfair business practices case brought by the Federal Trade Commission.
• Represented a major telecommunications company in connection with litigation over subpoenas issued by the U.S. House Select Committee on the January 6 Attack.
• Represented a global pharmaceutical manufacturer in a multifaceted Lanham Act case in the U.S. District Court for the Northern District of California, the U.S. Court of Appeals for the Ninth Circuit, and the Judicial Panel on Multidistrict Litigation.
• Obtained a writ of mandamus quashing a state trial court’s order requiring Sidley’s client to produce a privileged and highly confidential report of an outside counsel investigation.
• Successfully represented a Luxembourg-based holding company in obtaining dismissal of a multibillion-dollar fraud and breach of contract complaint in the New York Supreme Court, Commercial Division.

Daniel maintains an active pro bono practice on behalf of nonprofits, religious organizations, and individual civil rights plaintiffs. He has appeared as counsel in numerous religious liberty and First Amendment cases. Currently, Daniel is representing a Hassidic Jewish organization in a challenge to a local government’s decision to seize the client’s house of worship through eminent domain, and a Catholic diocese facing a eight-figure defamation claim brought by a suspended priest. Daniel has also supervised several briefs in connection with the Yale Law School Free Exercise Clinic.

Daniel has also been appointed as counsel by several appellate courts to represent indigent parties. These appointed representations include:

• Parker v. District of Columbia, 298 A.3d 785 (D.C. 2023), in which D.C.’s high court vacated the defendant’s convictions for armed robbery and possession of a firearm during a crime of violence.
• United States v. Helm, 58 F.4th 75 (2d Cir. 2022), which challenged the government’s conduct at sentencing and the district court’s application of the sentencing guidelines.
• Tolliver v. Noble, 752 Fed. App’x 254 (6th Cir. 2018), which reinstated an inmate’s challenge to prison officials’ allegedly retaliatory confiscation of his legal materials.

Additionally, Daniel was part of a trial team that secured a jury award of compensatory and punitive damages in a federal civil rights case alleging unconstitutionally excessive force in effecting arrest, and obtained compassionate release on behalf of a federal prisoner whose underlying health conditions placed him at serious risk from COVID-19.