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Louis H. (Louie) Castoria is a partner and a founder of the firm’s Appellate Team. On July 1, 2021, he achieved a victory in the Supreme Court of the United States in the landmark constitutional law case that upholds civil rights under the First Amendment, Thomas More Law Center v. Bonta, 594 U.S. __, S.Ct. docket 19-251.

Mr. Castoria represents and defends financial and professional services clients including accountants, lawyers, homeowners’ associations ( HOAs), insurance brokers, real estate agents and brokers, corporate directors and officers in private and public companies, and businesses covered under professional liability policies, in California and in matters under the Financial Industry Regulatory Authority (FINRA). Additionally, his practice includes securities and class action defense litigation including for  products to online businesses. He also represents insurance companies for coverage, monitoring, regulatory and litigating counsel, performs claims audits, and has written insurance policies.

Throughout his 40-year career Mr. Castoria has represented clients in appeals and petitions throughout California in federal and state courts, all six of California and all four federal judicial districts, as well as the California and United States Supreme Courts. He assists other lawyers in developing appellate strategies, and in conducting trials to better withstand appeals.

Defending the Constitution, and other appellate victories:

In a case spanning seven years, Mr. Castoria fought for the privacy rights of donors who contribute to charitable organizations. (Thomas More Law Center v. Bonta, 594 U.S. __, S.Ct. docket 19-251)  The California Attorney General (Kamala Harris, at the time) was requiring charitable non-profit organizations to divulge their lists of significant donors or face dire consequences. After urging the Attorney General’s office to desist, Mr. Castoria filed suit in the United States District Court for the Central District of California, seeking to enjoin the donor disclosure demands. The case went to trial, resulting in a victory for our client, Thomas More Law Center, which advocates for clients’ rights in courts throughout the country. On appeal, the Ninth Circuit Court of Appeals reversed, leaving the Supreme Court as the only hope to preserve donors’ rights of anonymous advocacy—a right the Founders relied on during the formative years of the United States. Though less than one percent of petitions to the Supreme Court each year are granted hearings, the Thomas More Law Center’s petition was sufficiently compelling to be accepted for consideration. After multiple layers of briefing, and with the backing of 40+ “friend of the court” briefs submitted by organizations and individuals across the political spectrum, the case was heard on April 26, 2021. Chief Justice John Roberts, writing for the 6-3 majority, struck down as facially unconstitutional California’s law requiring charities to disclose their major donors. This means that the ruling protects all donors in all states, not just our client.

Mr. Castoria recognizes that being an effective advocate requires a broad understanding of the client’s business or practice. Litigation sometimes exacerbates the client’s economic or regulatory exposure, so while a vigorous defense is needed, all options must be considered early in the case. Mr. Castoria’s problem-solving skills are often key to achieving favorable outcomes for his clients. As a California-trained mediator, he looks beyond “positions” to identify the core interests at stake, and follows the motto “Box? What box?”

Mr. Castoria is an award-winning writer. In his legal practice and frequent scholarly writings, he follows the journalistic edict “don’t bury the lede,” always conveying the essential information and the main argument at the outset. He also writes columns on E&O avoidance for National Underwriter Property & Casualty 360 Magazine and a quarterly column on E&O avoidance for the Daily Journal, California’s largest newspaper for the legal community. 

Public Service

A leader in education, Mr. Castoria has developed many continuing education programs for lawyers and other professionals. He teaches three law school classes as an adjunct professor at Golden Gate University, each course focusing on the “things they don’t teach in law school,” including the important role insurance plays in civil litigation. He has represented municipal school districts and higher education institutions in tort and employment matters. He is chairman emeritus of the Board of Directors of the Insurance Educational Association. He is a member of the Professional Liability Defense Federation and The Mediation Society.  He authored three chapters of Agents of America’s series, Insurance Agency Risk Management (Thomson Reuters, 2013 – 2014), and two units of the revised curriculum for the Registered Professional Liability Underwriter (RPLU) designation, at the request of the Professional Liability Underwriting Society (PLUS).

Mr. Castoria has lectured throughout the country on insurance, tort reform and technology issues. He has twice chaired the PLUS D&O West Symposium, chaired the PLUS Events Committee, and has served on the PLUS International Conference Committee. He is an invited lecturer at seminars sponsored by legal and insurance industry groups, including PLUS, the California State Bar Association, Insurance Brokers and Agents of the West, Institute for International Research, American Conference Institute, Insurance Federation of New York, and Pacific Claims Executive Association, among others. He also conducts mock trials at insurance industry and professional organization meetings, often illustrating how liability exposures to businesses, insurers, and reinsurers may be reduced.

Mr. Castoria is the founder and CEO of the Coastal Literary Arts Movement, a 501(c)(3) nonprofit that encourages multi-lingual literary appreciation and expression in rural coastal communities. He writes a weekly humor column for his local newspaper, the Half Moon Bay Review, and has done so for 25 years.


  • California
  • U.S. District Court
    • Central District of California
    • Eastern District of California
    • Northern District of California
    • Southern District of California
  • U.S. Court of Appeals
    • Ninth Circuit
  • United States Supreme Court


  • University of California, Berkeley – Mediation Training Certificate
  • University of California, Berkeley, School of Law – J.D.
  • University of San Francisco – B.A.

Professional Memberships

  • American Bar Association, Tort and Insurance Practice Section
  • California State Bar Association
  • Insurance Educational Association, Chairman, Board of Directors
  • Professional Liability Underwriting Society (PLUS)
  • Professional Liability Defense Federation

Representative Matters

  • Supervised and/or directly defended against scores of legal malpractice claims, ranging from complex commercial transactions to claims made in fee disputes.
  • Won a summary judgment for an international insurance brokerage firm that was accused of misrepresenting the coverage it had procured for a manufacturer of wind-turbine generators, with over $60 million in alleged out-of-pocket damages, and successfully argued the case on appeal to the Ninth Circuit.
  • Litigated civil rights cases involving First and Fourth Amendment rights, and fee awards under the Civil Rights Act.
  • Defended an accountant/financial planner in an investment and business venture case alleging erroneous reassurances of the tax treatment of a business venture and a stock loan program.
  • Won a defense arbitration award for a court-referee accountant who aided a couple in a contentious divorce. The award included payment by the plaintiffs of all defense fees and costs.
  • Investigated and resolved a massive fraud case arising from an individual broker’s submission of false invoices for commissions and fees.
  • Defended a tax accountant who allegedly gave erroneous advice regarding tax treatment of a VEBA multiemployer benefit plan.
  • Conducted reinsurance audits at major professional liability insurance companies.
  • Obtained a dismissal of a $17 million dollar claim against a brokerage firm arising from a business interruption claim by establishing that the firm did, in fact, procure insurance coverage.
  • Obtained summary judgment in the Central District of California on behalf of a reinsurer, and subsequently represented the client in obtaining an affirmance of the judgment in the Ninth Circuit.
  • Settled during trial a case arising from the defalcation of an in-house bookkeeper whose actions were not discovered during reviews of the company’s accounts.
  • Obtained summary judgment for a reinsurer that was sued for bad faith by an underlying claimant, and succeeded in having the judgment affirmed on appeal.
  • Obtained arbitration awards for reinsurers in two cases based on the ceding carriers’ failure to properly allocate claims to policy years, or to competently handle the underlying claim, resulting in an extra-contractual exposure that was not covered under the reinsurance treaty.
  • Served as outside counsel to the California State Bar Association, including working with actuaries at one of the world’s largest actuarial firms in developing and modifying insurance programs.
  • Represented an accountant who advised a single-employer medical plan about its required level of funding.
  • Advised the California State Bar’s Committee on Group Insurance Programs, and negotiated and drafted agreements on behalf of the Bar with large insurance brokerage firms and carriers with the Bar’s outside actuarial experts.


  • 2022, 5.0 AV Preeminent Rating by Martindale-Hubbell 
  • AV® Preeminent™ Rated by Martindale-Hubbell
  • Northern California Super Lawyers (2007 – 2016)



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