Daniel H. Leff

Daniel Leff is a litigator and a member of Nixon Peabody’s Government Investigations & White Collar Defense practice group.

What do you focus on?

I represent clients in all stages of government investigations and criminal and civil litigation.

I have guided clients from multiple industries—including pharmaceuticals and medical devices, energy, chemicals and refining, telecommunications and retail—facing criminal and regulatory scrutiny from state and federal agencies, including the U.S. departments of Justice, Agriculture and Interior; the Environmental Protection Agency (EPA); the Federal Trade Commission (FTC); the Federal Communications Commission (FCC) and the Federal Energy Regulatory Commission (FERC). At present, I spend much of my efforts representing companies and individuals facing investigation under the federal False Claims Act and Anti-Kickback Statute.

In addition to representing clients facing government scrutiny, I represent clients litigating against companies, individuals and nongovernmental organizations before courts, administrative tribunals and arbitral bodies. I have particular experience litigating issues under complex environmental, energy and antitrust statutes on the state, federal and international level.

I also have experience counseling and representing companies seeking government regulatory approvals—including successful buyers and sellers in antitrust reviews before the Department of Justice and FTC in connection with several multi-billion dollar mergers, energy companies before FERC and companies undergoing state and federal environmental and energy extraction permitting processes.

What do you see on the horizon?

I expect companies to see enforcement actions brought by a wider variety of government entities and plaintiffs—including various federal and state agencies, individuals and NGOs—each pursuing different goals and means.  Policy changes in the federal government may, for instance, be offset by an increase in state enforcement and suits by private groups and individuals acting under qui tam and citizen suit provisions. Companies must be prepared to react to investigations and actions begun by a diverse array of actors and must be able to navigate overlapping and potentially conflicting enforcement priorities.


Daniel H. Leff



Phone: 617-345-1383

Fax: 844-853-4957

New York University School of Law, J.D.

Georgetown University School of Foreign Service, B.S.F.S.


New York

District of Columbia

U.S. District Court, District of Massachusetts

U.S. District Court, District of the District of Columbia

Back to top