Image: William F. Sullivan

William F. Sullivan

Senior Counsel, Litigation Department


William Sullivan is senior counsel of Paul Hastings Litigation Department and is based in the firm's Los Angeles office. Mr. Sullivan has substantial experience in complex business litigation, including the representation of public companies in the defense of federal and state securities class actions, derivative actions and regulatory proceedings. Most of these cases involve claims arising out of public offerings, mergers and acquisitions, disclosure obligations, insider trading, accounting practices or allegations of breaches of fiduciary duties. Mr. Sullivan argued and won the ground-breaking Dura Pharmaceuticals case before the United States Supreme Court which established the standard for loss causation in federal securities class actions.  Mr. Sullivan is a veteran trial lawyer who has tried cases involving stock valuations, fraud, forgery, license agreements, internet contract issues, whistle blower claims, employee termination, lender liability, fiduciary duties and breach of real estate contracts, among others. Mr. Sullivan has significant experience counseling public companies and frequently counsels boards of directors in special investigations. Mr. Sullivan also represents clients before the Securities and Exchange Commission. Mr. Sullivan has substantial appellate experience, including before the United States Supreme Court.

Previously, Mr. Sullivan served as the Global Chair of the Litigation Department, Chair of the Los Angeles Litigation Department, and Chair of the firm's Securities Litigation practice.


  • Honored as "California Lawyer of the Year" in Securities Law
  • Recognized as one of the Top 30 Securities Litigators in California and one of the Top 100 Most Influential Lawyers in California
  • Honored as one of the Top 100 Lawyers in Los Angeles by The Los Angeles Business Journal
  • Recognized as a leader in his field by Chambers USA
  • Listed in The Best Lawyers in America and as a Legal Superstar in Securities Law 360


  • University of California at Los Angeles School of Law, J.D., 1977
  • University of California Berkeley, A.B., 1974 (with distinction)


  • Dura Pharmaceuticals, Inc. Securities Litigation: Mr. Sullivan argued this landmark case before the United States Supreme Court. This argument was noted as the most important securities litigation case argued before the Supreme Court in a decade. The unanimous decision in favor of Mr. Sullivan’s client is now the controlling case on loss causation. From the onset of the litigation, we represented Dura and its officers and directors in this consolidated federal court securities class action filed in the Southern District of California.
  • In re UBS Auction Rate Securities Litigation: We represented UBS in this high-profile series of cases involving auction rate securities arising out of the global credit crisis. These main cases are pending in the United States District Court for the Southern District of New York. Through a series of motions, we were able to defeat every claim and theory of liability that plaintiffs tried to allege against our clients. First, we obtained a defense judgment against claims brought under the Investment Advisers Act of 1940 and under New York state law. Next, we won a motion to dismiss claims brought under the Securities Exchange Act of 1934 based on our argument that the named plaintiffs could not establish compensable damages in the case -- a decision which was later followed in several other cases involving auction rate securities. Finally, when a new set of plaintiffs filed a new complaint based on yet another theory, the court again granted our motion to dismiss, agreeing with us that the plaintiffs' allegations could not support a claim for market manipulation. We also counsel UBS on numerous other related cases and arbitrations filed around the country, including one of the cases resulted in a dismissal of all claims and is reported at Kassover v. UBS AG, 619 F.Supp.2d 28 (S.D.N.Y. Dec 19, 2008). Our team obtained a key industry leading result for UBS. We had the first decision dismissing an ARS case and all the other investment banks used our motion as a model.
  • Jacobs Engineering: We represented the directors of Jacobs Engineering Group Inc., as well as the company’s executive compensation consultant, Frederic W. Cook & Co., Inc., in a shareholder derivative action. The shareholders claimed that the directors violated their fiduciary duties owed to Jacobs regarding the directors’ approval of the company’s executive compensation. The shareholders also claimed that Frederic W. Cook aided and abetted the alleged breach of fiduciary duty and breached its contract with Jacobs regarding its advice on Jacobs’ executive compensation. After hearing argument on the directors’ motion to dismiss, the Los Angeles Superior Court issued an order dismissing all claims and entered final judgment in favor of the defendants.
  • Morgan Stanley: We are representing Morgan Stanley, one of its officers, and several of its investment funds in a breach of fiduciary duty and fraud case brought in Honolulu, Hawaii by more than 50 plaintiffs, including the former governor of Hawaii, arising out of Morgan Stanley's investment in and subsequent sale of Pihana, Inc. Plaintiffs alleged damages against more than thirty total defendants in excess of US$500 million. The case has been pending for approximately two years and raised numerous issues of first legal impression, including the question of whether the internal affairs doctrine required application of Delaware law on the statute of limitations to the case brought in Hawaii. We successfully obtained dismissal of the case on limitations and other grounds and obtained an award of $1 million in attorneys' fees. We thereafter settled the case on favorable terms during an appeal to the Hawaii Supreme Court, and then defended the settlement against challenges by co-defendants in the trial court.
  • Boulder: United States District Court for the District of Colorado: We obtained dismissal on a motion to dismiss in favor of a mutual fund client and its independent directors of purported nationwide class action brought under the Investment Company Act of 1940 which sought to enjoin a rights offering to shareholders.
  • Countrywide: We represent several former senior executives of Countrywide Financial Corporation in numerous securities cases brought by plaintiffs across the country which had allegedly purchased, collectively, over a billion dollars worth of mortgage-backed securities issued by the company. In these matters, our clients, who had signed "shelf" registration statements underlying the mortgage-backed securities, faced claims for, inter alia, alleged violations of the federal securities laws, the Blue Sky laws of several states, and various common law claims. Through our creative and aggressive motion practice, our clients were dismissed entirely from eight district court cases and one 9th Circuit appeal case.
  • Emergent: Paul Hastings represented Emergent Group, Inc. and its former board members in three consolidated class action complaints filed in Los Angeles Superior Court on and after February 22, 2011. The lawsuits were filed in connection with the tender offer sale of Emergent to Universal Hospital Services, Inc. ("UHS"). The complaints each alleged that the individual defendants breached fiduciary duties owed to Emergent’s public shareholders by agreeing to a sale for an unfair price, with improper preclusive deal protection devices , and through a process that failed to maximize the value of Emergent to its public shareholders. The complaints sought, among other things, declaratory and injunctive relief including to prohibit the Defendants from consummating the transaction and other forms of equitable relief.
  • Universal: Paul Hastings represents Universal Entertainment Corporation ("Universal"), its wholly owned subsidiary, Aruze USA, Inc. ("Aruze USA"), and its Chairman and President, Kazuo Okada, in litigation involving a purported stock redemption by Wynn Resorts, Inc. ("Wynn Resorts") of Aruze USA’s $2.9 billion equity investment in Wynn Resorts. Immediately following the purported redemption, Wynn Resorts filed a complaint against Mr. Okada, Universal, and Aruze USA for declaratory relief and breach of fiduciary duty. On March 12, 2012, Universal and Aruze USA filed a counterclaim asserting, among other claims, violations of the Federal Securities Act of 1934 under the "forced seller" doctrine, related to the purported redemption, which would produce a massive, illegal windfall for Wynn Resorts.



    Engagement & Publications

    • Frequent panelist and speaker on litigation matters

    Practice Areas

    Investment Management
    Securities Litigation
    Class Actions
    Anti-corruption and FCPA
    Investigations and White Collar Defense
    White Collar Defense




    California Bar


    UCLA School of Law, J.D. 1977
    University of California, Berkeley, A.B. 1974

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