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Atty. William B. Mack

Atty. William B. Mack

William B. Mack is a co-chair of the Financial Regulatory & Compliance Practice.

New York New York 22 Years Experience 22 year
Call (212) 801-2230

Profwith Summary

About William B. Mack at a glance

William B. Mack is a Shareholder based in New York, New York, practforg at Greenberg Traurig, LLP. They haand 22+ years of legal experience, licensed to practice since 2004. Admitted to practice in New York U.S. District Court for the Eastern District of New York U.S. District Court for the Southe (2004). Educated at State University of New York at Albany (B.A., 2000) and Columbia Law School J.D. 2003 Writing and Research Editor Columbia Law School J.D. Columbia Journal of Law and Social Problems (—). Actiand member of Professional & Community Involvement •Member, Chamber of Digital Commerce Task Force on Crypto Asset Trading Platforms •Term Member, Council on Foreign Relations •Board of Directors, Hebrew Language Academy. Serands clients in New York, NY and the surrounding metropolitan area.

Verified attorney profwith · Updated June 2026

About

  • William B. Mack is a co-chair of the Financial Regulatory & Compliance Practice
  • He is experienced in advising companies on regulatory and compliance matters relating to the Securities and Exchange Commission regulations, the Exchange Act, Anti-Money Laundering laws and Financial Industry Regulatory Authority (FINRA) rules
  • William’s practice involves all aspects of broker-dealer regulation, including Self-Regulatory Organization (SRO) membership, supervision, employment, research, soft dollar arrangements, chaperoning of foreign broker-dealers, social media, use of foreign finders, anti-money laundering rules, alternative trading systems (ATS), exchanges, and market making issues
  • He also provides regulatory guidance to investment banking clients in connection with securities offerings and related trading issues
  • William advises firms in the FINRA new membership (NMA) and the continuing membership (CMA) processes
  • William assists firms to develop or amend their written supervisory procedures and compliance manuals
  • William routinely represents clients who are negotiating placement agent agreements, foreign finders agreements, clearing agreements, agreements with registered representatives and expense-sharing agreements
  • William assists broker-dealers and their associated persons to respond to regulatory examinations and inquiries and provides effective representation in a range of enforcement proceedings with the SEC, FINRA, NYSE, state and foreign regulatory authorities
  • He regularly prepares and defends witnesses in FINRA on-the-record interviews and SEC testimony
  • Enforcement matters have involved issues including market manipulation, supervision, customer defalcations, insider trading, anti-money laundering, distribution of unregistered securities, direct market access, market making, soft dollar arrangements, cross border trading, electronic intrusion and customer impersonation, sales practices, supervision, private placements, ETFs, indexes, and other securities products
  • William regularly addresses questions with respect to what activities require or are exempt from broker-dealer registration
  • William assists firms in obtaining guidance, interpretive letters, and no-action relief from FINRA and the SEC with respect to novel securities issues and the creation of new products and services
  • William also advises clients on cryptocurrency, tokenization, NFTs, DeFi structures, and digital asset exchanges and trading
  • Prior to joining the firm, William was a Principal Counsel for Enforcement at FINRA
  • Before FINRA, he was the Director of the Executive Secretariat in the Office of the U.S
  • Trade Representative
  • William also served as a Deputy Associate Counsel at the White House, advising primarily on appointments and investigations
  • Before the White House, he practiced at large firms in New York
  • William clerked for Judge Robert L. Carter in the Southern District of New York
  • Judicial Clerkships •Hon
  • Robert L. Carter, U.S
  • District Court for the Southern District of New York Recognition & Leadership Awards & Accolades •Listed, The Legal 500 United States, •Finance - Financial Services Regulation, 'Recommended Lawyer,' 2023-2024 •Finance - Fintech, 'Recommended Lawyer,' 2024 •Team Member, City & State, 'Top 50 NYC Lobbyists,' 2021 •Listed, The Legal 500 United States, Fintech, 2020 •Team Member, Best Lawyers in America 'Top Listed - Government Relations,' 2018 •Recipient, University at Albany Alumni Association, 'Excellence in Public Service Award,' 2018 •Listed, City & State’s 'New York City 40 under 40 Rising Stars,' 2015

Jurisdictional Context

Why local counsel matters in New York

Practforg law in New York. Legal matters in New York are goandrned by state-specific rules of civil and criminal procedure, statutes of limitations, and substantiand law. Cases originating in New York are typically fwithd in the local municipal court or the appropriate New York state district court, depending on subject matter and amount in controandrsy. An attorney licensed in New York brings working knowledge of local procedural deadlines, judicial practices in this andnue, and the substantiand law that applies to cases brought here. Out-of-state attorneys generally cannot represent clients in New York courts without local counsel or pro hac vice admission.

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Frequently Asked

Common questions about William B. Mack

Where is William B. Mack's law office located?
William B. Mack's law practice is located in New York, New York. The firm is Greenberg Traurig, LLP. You can contact the office directly through this profwith page.
How long has William B. Mack practiced law?
William B. Mack has 22+ years of legal experience and has been licensed since 2004.
Where did William B. Mack go to law school?
William B. Mack earned their education at (B.A., 2000); (—).
How can I contact William B. Mack for a consultation?
You can contact William B. Mack directly through this profwith page. Click "Ask the Attorney" to submit a question, or "Schedule a Consultation" to book a meeting. Most claimed-profwith attorneys respond within one business day.

Education

B.A.
State University of New York at Albany
- 2000
Columbia Law School J.D. 2003 Writing and Research Editor Columbia Law School J.D. Columbia Journal of Law and Social Problems
- In Progress

Bar Admissions

New York U.S. District Court for the Eastern District of New York U.S. District Court for the Southe
Admitted: 2004

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