Sidley Austin Expands Antitrust Bench with Addition of Mary Marks in NY

Sidley Austin LLP has brought on Mary Marks as a partner in its Antitrust and Competition practice in New York, further strengthening the firm’s transactional capabilities in a year marked by growth.

Marks, who joins from Davis Polk & Wardwell, focuses on advising clients on both U.S. and cross-border transactions. According to a statement from Sidley, her work involves securing regulatory clearance under the Hart-Scott-Rodino (HSR) Act and other global merger control frameworks. She also provides guidance on pre-transaction planning, coordination between merging parties, the exchange of sensitive information, and compliance with HSR filing requirements.

Read more: Sidley Ads Vadim Brusser as Antitrust Partner in DC

Per a statement from the firm, Marks’ arrival is the latest in a series of strategic hires that reinforce Sidley’s commitment to its Antitrust and Competition practice. Her addition follows the recent onboarding of other prominent lawyers in the field, including Elisabetta “Betta” Righini in Brussels and Vadim Brusser, Carrie Mahan, and Corey Roush in Washington, D.C.

This move also aligns with a broader expansion of Sidley’s New York operations. The firm noted that ten lateral partners have joined its M&A and Private Equity practice in 2025 alone, underscoring a concerted effort to deepen its bench in key transactional and advisory areas.

Source: Sidley