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Daniel Leff

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Daniel Leff is an antitrust litigator, trial lawyer, and strategic advisor. As a former state assistant attorney general, he draws on his experience litigating complex, high-profile antitrust cases for clients involved in or anticipating litigation as both plaintiffs and defendants. Dan also counsels and advocates for companies seeking antitrust regulatory approval for mergers, acquisitions, and innovative business deals.

Dan joined Crowell from the Massachusetts Attorney General's Office (AGO), where he served in the Office's Antitrust Division. In that role, he worked hand-in-hand with enforcers from the U.S. Department of Justice (DOJ), the Federal Trade Commission (FTC), and the attorney general offices of nearly every U.S. state and territory to investigate and litigate merger, monopolization, and cartel matters.

His work with the AGO included successfully trying merger and Sherman Act § 1 cases in federal court. He was also a lead member of a plaintiff group comprising nearly every state attorney general office in the country in a large pharmaceutical price-fixing multidistrict litigation (MDL).

Dan also investigated, litigated, and settled numerous competition matters in industries including telecommunications, transportation, energy, agricultural products, healthcare, and pharmaceuticals. Clients benefit from Dan's experience in the Sherman, Clayton, and FTC acts and numerous state antitrust and consumer protection statutes, as well as his familiarity with the perspectives of state and federal enforcers across the country.

Dan began his career at Crowell, where he represented clients facing federal and state antitrust, consumer protection, and environmental scrutiny, primarily in the telecommunications and energy industries. He also previously worked for an international law firm in Boston, representing pharmaceutical and medical device companies facing federal civil and criminal investigations.

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Each week, Crowell & Moring’s State Attorneys General team highlights significant actions that State AGs have taken. See our State Attorneys General page for more insights. Below are the updates from May 22-28, 2025

Multistate

  • A multistate coalition of 20 attorneys general filed for injunctions preventing the Department of Homeland Security (DHS) and the U.S. Department of Transportation (USDOT) from withholding federal funds that would otherwise be granted to states in response, allegedly due to the states’ refusal to cooperate with federal immigration enforcement initiatives. The coalition alleges that the withheld funds aid state law enforcement, counterterrorism, emergency services, disaster preparation and relief, repairs to crumbling transportation infrastructure, and transit improvements. Each agency has recently imposed additional conditionsFed on federal funding, such as a requirement that recipients assist in enforcing federal immigration law. The coalition argues that the conditions exceed DHS’s legal authority and further, that immigration is unrelated to the funds at issue.

Continue Reading State AG News: Emissions Standards, Federal Funding, Consumer Protection May 22-28, 2025

State Attorneys General are targeting unfair trade practices in automobile sales, including many of the sales tactics that would have been prohibited under the FTC’s now-vacated CARS Rule. Click here to continue reading the full version of this alert.

Each week, Crowell & Moring’s State Attorneys General team highlights significant actions that State AGs have taken. See our State Attorneys General page for more insights. Below are the highlights from April 3-9, 2025.

Multistate
• 12 state attorneys general sent letters to twenty law firms demanding that the firms comply with the U.S. Equal Employment Opportunity Commission’s (“EEOC”) March 17 letter requesting information to determine whether the law firms had engaged in any illegal and discriminatory actions through their diversity, equity, and inclusion (“DEI”)-related employment policies.Continue Reading State AG News: Labor & Employment, State AG Office News, Consumer Protection April 3-9, 2025

Each week, Crowell & Moring’s State Attorneys General team highlights significant actions that State AGs have taken. See our State Attorneys General page for more insights. Here are last week’s updates.Continue Reading State AG News: Consumer Protection, Diversity, Education, Healthcare Feb. 28-March 6, 2025

  • Key takeaway #1 States and their attorneys general have increasingly prioritized antitrust enforcement and policy, with several adopting or proposing new pre-transaction notice requirements and other more expansive antitrust laws.
  • Key takeaway #2 Early efforts have focused primarily on the healthcare industry, but that focus is poised to expand.
  • Key takeaway #3 The new state laws and proposals stand to complicate regulatory requirements for businesses contemplating mergers and acquisitions, and could expose companies to increased investigations and litigation by public and private entities.

Continue Reading The States Step Up to the Plate: Several States Adopt and Propose New Pre-Transaction Notice Requirements and Other Antitrust Laws

Each week, Crowell & Moring’s State Attorneys General team highlights significant actions that State AGs have taken. See our State Attorneys General page for more insights. Here are last week’s updates.Continue Reading State AG Updates: January 23-February 5, 2025

Key takeaway #1 Expect State Attorney General antitrust enforcement to increase in the coming four years.

Key takeaway #2 Both Democratic and Republican AGs will be active, separately and on a bipartisan basis.

Key takeaway #3 AGs likely to focus on tech, healthcare, consumer goods, labor, and ESG and DEI initiatives.

With the coming of the new presidential administration, state antitrust enforcement is poised to intensify. We expect both Republican and Democratic Attorneys General (AGs) to actively pursue antitrust investigations and litigation. They will fill in where the U.S. Department of Justice and Federal Trade Commission reduce focus but are also sure to work, including on a bipartisan basis, with their federal counterparts. Below, we explore how state AGs are likely to shape the antitrust landscape in the coming four years, and the areas where we anticipate significant enforcement activity.Continue Reading State Antitrust Enforcement: A Continued Focus on Competition During the New Administration

Each week, Crowell & Moring’s State Attorneys General team highlights significant actions that State AGs have taken. See our State Attorneys General page for more insights. Here are last week’s updates.Continue Reading State AG Updates: December 26-January 1, 2025

Each week, Crowell & Moring’s State Attorneys General team highlights significant actions that State AGs have taken. See our State Attorneys General page for more insights. Here are last week’s updates.Continue Reading State AG Updates: November 28-December 11, 2024