Mary Ellen Callahan is an American attorney who served as the Assistant Secretary for the DHS Countering Weapons of Mass Destruction (CWMD) Office from August 2023 to January 2025.

[4] Callahan was a student in Barack Obama's classes at the University of Chicago Law School and has spoken with the New York Times[5] and the Washington Post about her impressions of him.

[6] Callahan began her legal career with an immediate focus on public service and consumer protection, and quickly became a leading expert and advocate in the (then) emerging area of data privacy and cybersecurity law.

In 2009, Callahan was appointed by Secretary Janet Napolitano to serve as Chief Privacy Officer of the United States Department of Homeland Security (DHS).

[9][10] At Jenner, Callahan applied her unique and broad experience to advise an array of clients across a spectrum of industries on issues at the interface of privacy protection with cybersecurity and national security.

[14] CWMD leads the Department's efforts and coordinated with domestic and international partners to safeguard the United States against chemical, biological, radiological, and nuclear (CBRN) threats.

14110 on Safe, Secure, and Trustworthy Development and Use of Artificial Intelligence CWMD also wrote and released a first-of-its kind report evaluating the potential for AI to be misused to enable the development of production of Chemical, Biological, Radiological, and Nuclear (CBRN) threats, while also considering the benefits and application of AI to counter them.

To qualify for the Order of the Dragon, civilians must have demonstrated the highest standards of integrity and moral character, and outstanding degree of professional competence, and have contributed to the promotion of the Chemical Corps in numerous ways over the course of their career.