Marguerite Z. Hammes

Tel | 414.276.5000




  • Georgetown University Law Center
  • University of Alabama (B.A., summa cum laude)

Marguerite Z. Hammes

Marguerite’s broad experience as a litigator, a transactional attorney, and as in-house counsel is of value to clients operating in regulated industries, whether involved in sophisticated commercial transactions, complex disputes, or regulatory compliance efforts. Marguerite’s prior clients in the health care and energy industries range from the start-up phase through Fortune 100 ranked companies. Relevant experience includes entity formation, complex financing transactions, internal and government investigations, litigation and bankruptcy proceedings. Significant experience navigating the complexities of health care delivery and information systems makes Marguerite uniquely qualified to assist clients in the health care sector. Prior to working for O’Neil, Cannon, Hollman, DeJong & Laing S.C., Marguerite worked as an associate for Foley & Lardner LLP in Milwaukee, Wisconsin, and Fulbright & Jaworski LLP in Texas and Washington, D.C.

Marguerite Assists Clients With

  • Corporate Governance
  • Confidentiality and Non-Disclosure Agreements
  • Due Diligence for Complex Financing Agreements
  • Regulatory Compliance and Internal Investigations
  • Health Care Litigation

Experience/Representative Client Work

  • Start-Ups, Early Stage and Emerging Growth Companies
    • Business entity selection and formation
    • Confidentiality and non-disclosure agreements
    • Factual analysis for patent applications and regulatory compliance
    • Financing agreements, direct sales agreements, and construction agreements
    • Evaluation for conducting business in foreign markets and FCPA compliance
    • Risk analysis for corporate restructuring proposals
  • Litigation and Government Investigations
    • Internal investigations relating to securities fraud, health care fraud and abuse regulations, and international commercial fraud
    • Health care compliance and litigation
    • Complex bankruptcy proceedings

Professional Associations & Affiliations

  • State Bar of Wisconsin
  • American Bar Association, Health Law & Life Sciences
  • Milwaukee Bar Association
  • American Health Lawyer’s Association
  • Health Care Compliance Association

Court Admissions

  • Wisconsin
  • United States District Court for the Eastern District of Wisconsin


  • Articles Editor, Georgetown Journal of Legal Ethics; Authored “No Contact Rule in the Civil Context,” Geo. J. Legal Ethics, Vol. XIV. No. 4 (2001)

Community Involvement

  • Solutions for Patient Safety, Patient Advocate for Ambulatory Safety Workgroup
  • Children’s Hospital of Wisconsin, Patient Advocate Volunteer
    • Medication Reconciliation (2016 to present)
    • Discharge Optimization (2016–2019)
    • Imaging Quality Assurance (2013–2018)
    • Discharge Order Set/Inpatient After Visit Summary Review (2015–2016)
    • Appendicitis Quality Improvement (2017–2018)
    • Family Advisory Committee (2016–2018)
  • Saint Francis Children’s Center, Board of Directors, Vice President (2016–2018)