Representing Labor Unions & Their Members

Sheridan, John P.

  • Principal


New York, NY






John has over twenty years of experience representing labor unions and Taft-Hartley benefit funds in state and federal courts and before administrative agencies and arbitration tribunals in disputes related to the NLRA, the LMRDA, ERISA, union trusteeships, union discipline, contractual grievances, harassment and discrimination, retaliation, and alleged denial of benefits. John represents his union clients in labor-related matters, including arbitration, the defense of unfair labor practice charges, and collective bargaining negotiations. He also assists his union clients with compliance with the LMRDA.

John also has an active litigation practice in both state and federal court and before administrative agencies. He has litigated LMRA, LMRDA, ERISA and employment law cases on behalf of unions and Taft-Hartley benefit funds. He represents his clients at all stages of litigation including pleading, discovery, dispositive motions, trials and appeals. John has argued appeals before the United States Court of Appeals for the First, Second, and Third Circuits. He has also handled proceedings before administrative agencies including the NLRB, state labor relations agencies, and state civil rights divisions. John has also appeared before grievance arbitrators on behalf of unions in disciplinary disputes. In addition to counseling labor unions regarding labor management issues, John also counsels unions regarding LMRDA compliance and has conducted training seminars for his union clients.

John assists his benefit fund clients with the development, administration, and governance of ERISA-qualified, multiemployer plans, including complying with ERISA's fiduciary duty provisions and its reporting and disclosure requirements. Before joining Marrinan & Mazzola Mardon, John worked in the labor and employment department in a large firm in New Jersey, and prior to that, he worked for a union-side law firm in Boston, Massachusetts.

Areas Of Practice

  • Labor
  • Employment
  • Litigation

Bar Admissions

  • Massachusetts, 1994
  • U.S. District Court District of Massachusetts, 1995
  • New Jersey, 1998
  • U.S. District Court District of New Jersey, 1998
  • New York, 2001
  • U.S. District Court Southern District of New York, 2002
  • U.S. District Court Eastern District of New York, 2003
  • U.S. Court of Appeals District of Columbia Circuit, 2003
  • U.S. Court of Appeals 3rd Circuit, 2005
  • U.S. Court of Appeals 2nd Circuit, 2006
  • U.S. Court of Appeals 4th Circuit, 2006
  • U.S. Court of Appeals 1st Circuit, 1997


  • Boston College Law School, Boston, Massachusetts
    • 1994
  • Harvard College
    • 1990
    • Honors: cum laude

Representative Cases

  • Unión De Empleados De Muelles De Puerto Rico, Inc. v. International Longshoremen's Association, 884 F.3d 48 (1st Cir. 2018)
  • Eddie Knight; Charles S. Miller–Bey; Eddie McBride; Leonard Riley, Jr. v. International Longshoremen's Association, 527 Fed.Appx. 187 (3d Cir. 2013)

Professional Associations And Memberships

  • New York City Bar Association

Practice Areas

Labor Law

Employee Benefits & ERISA