Our lawyers have firsthand experience in national security programs and policies at the most senior levels of the US government. Mayer Brown's National Security practice advises clients on a wide spectrum of matters that involve sensitive national security issues. We have extensive experience working with the Department of Defense (DOD), as well as the Departments of State, the Treasury, Justice (DOJ), and Homeland Security (DHS); with federal law enforcement, intelligence, and military agencies such as the Federal Bureau of Investigation (FBI), Central Intelligence Agency (CIA), and National Security Agency (NSA); and with the increasing number of government entities that play a growing role in US national security today on issues ranging from energy to technology to trade.

Our team assists companies as they engage with US government agencies and officials, navigate the global security environment, and grapple with laws, policies, and regulations aimed at addressing evolving threats and technologies. We represent clients supporting critical programs and missions in defense, homeland security, space, energy, and cybersecurity, as well as in matters involving sanctions and export controls, anti-corruption, immigration, and transactions subject to the Exon-Florio Amendment to the Defense Production Act of 1950.

Many of our lawyers have firsthand experience in national security programs and policies at the most senior levels of the US government, including the White House, DOD, DOJ, Department of the Treasury, Department of Commerce, FBI, NSA, Congress and US Attorneys’ offices around the country. Some of these positions include:

  • Former Commissioner on the bipartisan National Commission on Terrorist Attacks Upon the United States (“9/11 Commission”)
  • Former US Secretary of Commerce
  • Former US Ambassador to Romania
  • Former Deputy General Counsel, US Department of Defense
  • Former Counsel, US Senate Select Committee on Intelligence
  • Former Commissioner, The William H. Webster Commission on the Federal Bureau of Investigation, Counterterrorism Intelligence, and the Events at Fort Hood, Texas, on November 5, 2009
  • Former US Deputy Secretary of Commerce
  • Former General Counsel, US National Security Agency
  • Former Member of the Board of Directors, Overseas Private Investment Corporation
  • Two former General Counsels, US Department of Commerce
  • Current Chairman of the US-Iraq Business Dialogue
  • Former Special Assistant to the Director of the Federal Bureau of Investigation
  • Former General Counsel, US Immigration and Naturalization Service
  • Former Deputy Assistant to the President and Staff Secretary
  • Former Chief Counsel, US Senate Judiciary Committee, Subcommittee on Crime and Terrorism
  • Two former US Trade Representatives
  • Former Counsel, US Senate Committee on Homeland Security and Governmental Affairs
  • Former Deputy General Counsel, Department of Commerce
  • Former General Counsel, Commission on the Prevention of the Proliferation of Weapons of Mass Destruction and Terrorism
  • Former Representative of the Sixth Congressional District of Connecticut, US House of Representatives
  • Former Chair of the Section 1423 Panel (the Acquisition Advisory Panel) responsible for rewriting federal procurement laws

Several members of the practice currently maintain high-level security clearances in the US government, which allows Mayer Brown to represent clients in high-stakes matters that involve classified information. We are one of the few firms with litigators who have both the clearances and the experience required to handle such matters. We also have extensive experience with matters before the military and intelligence agencies within DOD.

National Security Policy, Legislation and Regulation

We are able to use sophisticated political experience and in-depth legal knowledge to advise clients on US defense and homeland security policy, legislation and regulation. We advise multinational businesses on national, state and local government issues, and we develop advanced legislative and regulatory strategies that address emerging issues across major industries. We have advised clients in need of multifaceted strategies to mitigate the political and economic risk inherent in conducting business with defense and security agencies and have engaged with US government entities seeking novel solutions to difficult challenges. We have represented clients and witnesses before congressional committee hearings and counseled clients on appropriate responses to congressional subpoenas and document requests. 

Government Contracts

Our lawyers have the optimum balance of skills and seniority levels needed to address the legal and business challenges our clients face in conducting business with departments and agencies involved in national defense and security. These challenges include complying with disclosure obligations, responding to audits and investigations, conducting internal investigation, and litigating disputes, bid protests and false claims actions. We have represented clients in national security-related contracting matters involving DOD, DHS, the Intelligence Community and other US departments and agencies raising issues involving, for example, defense hardware and platforms, services support, space missions and research and development. We counsel clients on issues arising out of the US government’s efforts to fight terrorism militarily or with respect to cybersecurity and biodefense contracting. We assist clients on the supply chain implications of restrictive federal procurement rules and policies affecting trafficking in persons and counterfeit parts, as well as compliance with socioeconomic requirements. In addition, we assist with transactions involving foreign buyers of US companies or assets and compliance with the requirements of defense agencies, Exon-Florio, export controls and the FCPA. We are regularly involved in procurement policy and regulatory issues involving defense, aerospace, homeland security and cybersecurity. 

Cybersecurity and Data Privacy

We advise clients on dynamic legal and policy issues involving cybersecurity and data privacy that implicate novel technology, national security, law enforcement and regulatory elements. Our experienced lawyers come from a range of disciplines, including regulatory, intellectual property, litigation, government, financial services regulation and enforcement, employment and business and technology sourcing. We help clients from all over the world comply with myriad data privacy and security regulatory obligations while minimizing risk and maximizing business opportunities in a constantly evolving threat environment. We provide strategic counsel in the following key areas: security incident preparation and breach response; litigation; strategic counseling and corporate governance; vendor and supply chain management, contracting and data transfers; regulatory and compliance; and policy and advocacy. 

Sanctions and Export Controls

We advise clients around the world on cutting-edge issues involving US sanctions on Iran and Russia, as well as the many other restrictions on international trade and investment imposed for US national security and foreign policy reasons. We also assist clients with market access issues related to the easing of US sanctions and restrictions against Cuba. In this frequently changing field, we guide clients through the complex intersection of US policy, US sanctions laws and export controls, and attendant business risks and opportunities. Our clients span all industry sectors, and include banks, consulting firms and manufacturers in the United States and abroad.

Through our frequent contact with export control and sanctions regulators, we understand how agencies may interpret and enforce regulations in specific circumstances. We advise clients on US export and re-export restrictions, including compliance with the Export Administration Regulations (EAR) governing dual-use exports, the International Traffic in Arms Regulations (ITAR) governing the export of defense articles and services, and restrictions implemented by the Office of Foreign Assets Control (OFAC) on dealings with sanctioned countries and trading partners.

CFIUS and National Security Restrictions on Foreign Investment

We assist clients in the United States and other countries with navigating the US national security restrictions on foreign investments in the United States. Many of these investments are subject to review to determine whether they threaten to impair US national security. Our lawyers understand the full range of these restrictions and the nature of reviews conducted by the Committee on Foreign Investment in the United States (CFIUS) or as they arise under Exon-Florio.

We have advised clients on how to structure transactions to mitigate national security concerns while achieving business objectives, and we have helped clients establish compliance programs to govern classified facilities, cleared personnel, sensitive technologies and other elements of a US business that may pose security concerns. Several of our lawyers worked directly on significant CFIUS and Exon-Florio matters while serving in senior government positions at DOD and the Department of Commerce. Our lawyers have substantial experience working with defense agencies and companies that have defense contracts involved in acquisitions.

Cross-Border Investigations and Anti-Corruption

Our lawyers offer clients all-encompassing solutions to ensure compliance with an increasingly global framework of highly complex investigations and sophisticated regulators that are becoming more prevalent throughout the world. Our experience includes defending civil and criminal enforcement actions involving the extraterritorial application of US laws such as the FCPA, OFAC sanctions and related criminal prohibitions, the USA PATRIOT Act, money laundering prohibitions and politically exposed persons (PEP) regulations/guidance, the Racketeering Influenced and Corrupt Organizations Act (RICO), the Anti-Terrorism Act and the Alien Tort Claims Act. Working seamlessly with our colleagues in offices around the world, we advise on the complex, consequential and potentially global ramifications of cross-border investigations. The issues that we have confronted include data practices, state secrets, cultural differences in business, attorney-client privilege and labor and employment practices and protections, as well as the interplay of foreign countries’ laws with US domestic laws. 

Immigration and Visa Issues

Our team manages not just visa and work permit authorizations, but the full gamut of global mobility issues impacted by US national security policies and regulations that our clients face on a daily basis. We assist clients (frequently on an enterprise-wide basis) with the necessary visa filings for their global offices. In complex cases, and in jurisdictions in which quotas or other local restrictions may apply, we provide customized counsel and identify the appropriate strategy for maximizing the chance of a successful submission. In some cases, this includes advising on the nature of the employment agreement or the company’s authorization to sponsor foreign workers in the United States. We are similarly accustomed to addressing complex personal challenges that may impact eligibility (e.g., prior visa denials, arrest records, serious medical issues and divorce or custody issues). 


  • Representing an individual criminal defendant in connection with presidential commutation related to US-Iran diplomatic negotiations.
  • Represented a contractor in litigation with respect to development and deployment of a new-generation, three-dimensional long-range expeditionary radar.
  • Advise a global petrochemical company on compliance with the US sanctions and export controls on Iran.
  • Represented a contractor in litigation with regarding design and development of a new long-range anti-ship missile.
  • Defended a former DOD procurement officer against charges of espionage.
  • Representing a contractor in a dispute involving the development and deployment of the US Army’s next-generation tactical vehicle.
  • Served as lead counsel in DOJ criminal investigation of the security contractor alleging violations of the federal export control laws and firearms laws related to the provision of services to the US government as well as efforts to obtain business in other parts of the world.
  • Representing a contractor in litigation involving fixed-wing pilot training for the US Army.
  • Advise a major global consulting firm, and its related entities worldwide, on compliance with US sanctions and export controls.
  • Represented a contractor in a dispute involving the operation and management of national nuclear weapons complex facilities.
  • Represented US military officers in connection with US Senate investigation arising out of the use of enhanced interrogation techniques.
  • Represented a contractor in litigation regarding a contract for the management and operation of US Air Force space launch sites.
  • Advised a foreign buyer with respect to acquisition of a US firm providing defense services, including negotiations with the Defense Security Service and CFIUS.
  • Represented a contractor in litigation involving a contract for collection and analysis of immigration data.
  • Represented a US energy technology firm in the CFIUS review of its joint venture with a Chinese state-owned enterprise, and developed anti-corruption, sanctions, export control and antiboycott compliance programs for the joint venture.
  • Represented a contractor in litigation concerning a contract for operation of a US Army ammunition plant.
  • Represented a US security contractor involved in providing security training to foreign law enforcement personnel at a Middle East facility built by the US government in connection with. a grand jury investigation based on allegations that the contractor was providing ITAR-controlled military training without obtaining the required export licenses from the US Department of State.
  • Advised a contractor with respect to various programs involving space systems.
  • Advising an international hospitality company in connection with licensing requirements to expand business operations into Cuba.
  • Advised a contractor with respect to compliance with DOD’s Mandatory Disclosure Rule involving defense articles.
  • Represented a contractor with respect to litigation involving systems to process and protect data regarding government benefits for the elderly and disabled.
  • Represented a security contractor in a series of matters arising from the firefight that arose in Nisur Square in Baghdad in 2007.
  • Represented a security contractor in connection with the federal inquiry into the September 2013 fatal shooting at the Navy Yard in Washington DC, including parallel investigations by the FBI, the Secretary of the Navy and Congress.
  • Represented a leading European financial services firm in the CFIUS review of its multi-billion-dollar merger with a US counterpart.
  • Represented a Cayman Island hedge fund in a successful challenge to a restraining order issued at a foreign government’s request under the USA PATRIOT Act.
  • Advising multiple companies on best practices to establish a managed services program to oversee the hiring and mobility of talent across borders, the required employment, benefits and immigration processes to optimize the program and the impact of export control, FCPA, and data protection regulations on their immigration and mobility programs.
  • Assisted a foreign financial institution in its internal investigation of possible violations of US restrictions on dealings with nationals or enterprises of Cuba, Iran, Sudan and Syria.
  • Representing a foreign government in its dealings with DOJ relating to the foreign government’s efforts to repatriate the “Bahia Emerald.”