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William Mack

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.

On May 19, 2026, the CFTC’s Division of Enforcement replaced its 2025 tiered scoring matrix with a declination-first framework that imposes heightened self-reporting, cooperation, remediation, and restitution requirements on registrants seeking enforcement credit.

Continue Reading CFTC Division of Enforcement Issues New Cooperation Policy

On May 18, 2026, the SEC rescinded Rule 202.5(e), ending its decades-old prohibition on post-settlement public denials by settling parties. This shift removes a longstanding settlement friction point and may affect how companies and individuals approach SEC enforcement matters, public communications, and parallel litigation.

Continue Reading SEC Rescinds Longstanding ‘No-Deny’ Settlement Policy in Enforcement Actions

On December 9, 2025, the Financial Industry Regulatory Authority (FINRA) released both its 2026 FINRA Annual Regulatory Oversight Report (the “Report”), and a companion FINRA Unscripted podcast (the “Podcast”), featuring senior FINRA leaders providing insights about the Report. Continue Reading Providing Useful Tools: FINRA Releases its 2026 Annual Regulatory Oversight Report, Together with a FINRA Unscripted Podcast Filled with Senior Leadership Insights

On Nov. 17, 2025, the U.S. Securities and Exchange Commission (SEC) issued a No-Action Letter confirming that it will not recommend enforcement action if a registered representative-owned personal services entity

Continue Reading Path Cleared for Registered Representative-Owned PSEs To Receive Transaction-Based Compensation

On March 12, 2025, the Financial Industry Regulatory Authority (FINRA) issued Regulatory Notice 25-04, seeking public comment on its initiative to modernize regulatory requirements for Members and Associated Persons.
Continue Reading With an Eye Toward Modernization, FINRA Requests Comment on Its Regulatory Requirements for Members and Associated Persons

On Feb. 25, the CFTC’s Division of Enforcement released an advisory highlighting the benefits of self-reporting, cooperation, and remediation for violations of the Commodities Exchange Act. It refines the Division’s approach, guiding how these factors influence enforcement recommendations.

Continue Reading CFTC Issues Enforcement Advisory on Benefits of Self-Reporting, Cooperation, and Remediation

Regulations amending Chapter 517 of the Florida Securities and Investor Protection Act (FSIPA) took effect Oct. 1, 2024 (the Regulations). While the Regulations revise certain existing securities and transactional exemptions

Continue Reading Florida Amends Securities and Investor Protection Act: Key Changes to Private Placement, Institutional Investor Exemptions