Sonja Arndt-Johnson is a Special Counsel at Buchalter and a member of the firm's White Collar & Investigations (WCI) and Privacy & Data Security practice groups. She presently serves as the WCI's Administrative Chair and the San Francisco Office's Administrative Litigation Chair. A former federal and local prosecutor, congressional advisor, and Fortune 500 secondee, she advises companies, executives, and individuals facing government investigations, regulatory enforcement actions, cybersecurity incidents, privacy matters, and other high-stakes disputes.

Drawing on experience with the U.S. Department of Justice-including the U.S. Attorney's Office for the District of Columbia, the Office of International Affairs, and the Computer Crime and Intellectual Property Section-as well as the Santa Clara County District Attorney's Office, Ms. Arndt-Johnson provides strategic counsel at the intersection of legal, business, and reputational risk. Before entering the legal profession, she advised Members of Congress on foreign affairs, national security, military, and veterans affairs issues, providing her with a unique perspective on the governmental and geopolitical dynamics that shape complex matters.

Clients value her strategic judgment, discretion, and practical, business-focused approach to matters with significant legal, financial, and reputational consequences.

Ms. Arndt- Johnson has received a number of prestigious awards, including:

"Top 500 Leading Global Investigations Lawyer," Lawdragon

"Top 40 Under 40," Daily Journal

Languages
German

Bar Admissions
State of California

U.S. District Court for the Northern District of California

U.S. District Court for the Central District of California

U.S. District Court for the Eastern District of California

U.S. Court of International Trade

U.S. Tax Court

Education
University of California College of the Law, San Francisco, J.D. - Editor in Chief of the Hastings Women's Law Journal

U.S. Army War College, National Security Seminar (NSS), Carlisle, PA

University of California, Santa Cruz, B.A., Business Management Economics and Politics - Study abroad: The Chinese University of Hong Kong

Significant Accomplishments

Recent

• Counsel for a lifestyle company, defending against a fraud prosecution in the Central District of California (Los Angeles), as well as a parallel SEC enforcement proceeding pending in the Southern District of New York (Manhattan).
• Counsel representing the most prominent cryptocurrency tax case on record. The politically motivated charges concern tax evasion arising from bitcoin holdings prior to expatriation from the United States.
• Counsel representing a Canadian encrypted phone and messaging provider and its CEO, who were indicted on charges of the Racketeer Influenced and Corrupt Organizations Act (RICO) violations and money laundering offenses stemming from the sale of encrypted phones, with revenues allegedly exceeding $100 million.
• Counsel representing one of the largest PVC-pipe manufacturers in the U.S. in connection with a RICO and fraud lawsuit for sham claims asserted by one of the largest plaintiff's asbestos law firms in the U.S.
• Counsel for a medical practice group and certain affiliated owners in one of the largest California-based healthcare qui tam lawsuits involving personal injury medical lien-based services and procedures pursued by State Farm in 2024. Investigated and resolved litigation against all clients within 90 days with a complete release of liability for all clients.

White-Collar

• Counsel for a Texas oil investor facing wire fraud allegations.
• Counsel for a San Francisco businessman facing wire fraud allegations in relation to an alleged political corruption kickback scheme.
• Counsel for a group of California businessmen facing international import crimes and related fraud allegations.
• Counsel for a CEO facing fraud allegations by the Office of Institutional Integrity (OII).

Investigations

• Counsel for companies facing California Greenwashing Taskforce investigations.
• Counsel for Chinese-based companies facing Department of Defense (DoD) and Department of Justice (DoJ) investigations.
• Counsel for for-profit and non-profit clients facing FTC investigations and related discovery requests.

Class Actions

• Counsel for a retail client facing an Unlawful Trade Practice Act (UTPA) class action before the Oregon Supreme Court.
• Counsel for a corporation facing an ERISA class action before the Second Circuit.
• Counsel for a university facing a Title IX class action in San Francisco.
• Counsel for a retail client in summary judgment proceedings related to a Washington Consumer Protection Act (CPA) class action.
• Counsel for multiple corporate clients having class action lawsuits in relation to wiretap claims as it relates to Chatbots and session replay software.

Judgement Enforcement

• Counsel for a Korean-based client on an arbitration clause enforcement issue.
• Counsel for a corporation client facing a judgment enforcement demand in relation to a commodities fraud allegation involving Bitcoin.

Other Experience

• Counsel for a telecommunications company for an emergency cease and desist request in relation to state wiretap violations.
• Secondee at Airbnb working on legal policy matters.
• Counsel for multiple retail clients on multi-state data breach reporting and notification compliance, federal health breach notification compliance, and contractual obligations under the Payment Card Industry (PCI) guidelines.

Professional Activities and Experience

• Community Enhancement Award, Aptos Chamber of Commerce
• S. Army Fort Hunter Liggett: Women's History Month Keynote Speaker
• 2014 Awardee, Disabled American Veterans, Chapter 85
• CALI Award: Criminal Law Seminar, UC College of the Law, San Francisco (formerly UC Hastings)
• Best Appellate Advocacy, UC College of the Law, San Francisco (formerly UC Hastings)
• Chancellor's Achievement Award for Diversity, UC Santa Cruz

Civility Versus Zealous Advocacy: An Attorney's Duty

Civility Versus Zealous Advocacy: An Attorney's Duty

Sonja Arndt-Johnson, Presenter on ABA Podcast

Sonja Arndt-Johnson, Panelist at Protecting Yourself and Your Business in the Digital Age Event

U.S. Supreme Court Strikes Down IEEPA Tariffs: Key Implications and Next Steps for Businesses

After Learning Resources v. Trump: Strategic Paths to Recovering Unliquidated IEEPA Tariffs Through Post-Summary Corrections

One Small Step for Importers: Federal Circuit Clears the Way for IEEPA Tariff Refund Litigation to Resume

CIT Orders CBP to Remove IEEPA Tariffs from Unliquidated Entries - Pressure Builds on CBP to Roll Out a Refund Procedure.

CIT Hits Pause on Immediate IEEPA Tariff Relief While CBP Builds Refund Process

Preserve Your Rights or Pay the Price: CIT Urges Importers to File Protests to Protect Liquidated IEEPA Refund Claims Still Eligible for Protest.

Sonja Arndt‑Johnson Serves as Panelist at BMO's "Protecting Yourself and Your Business in the Digital Age" Event, Co‑Sponsored by Buchalter

GM Privacy Penalty Signals A Change In Calif. Enforcement