Biography
Colleen Sinzdak is currently a partner in the Appellate and Supreme Court practice at Milbank LLP. At Milbank, Colleen has worked on major Supreme Court cases, including VOS Selections v. Trump (the tariffs case) and Wolford v. Lopez (the defense of a Hawaii gun law against a Second Amendment challenge). Colleen has also been litigating on behalf of various parties challenging or defending against recent federal government initiatives, including DOT’s suspension of funding for the Hudson Tunnel Project, DOJ’s suits against cities that have elected not to cooperate with ICE, and DOJ’s subpoenas to children’s hospitals in connection with their treatment facilities for transgender youth. In addition, Colleen has worked on a variety of high stakes bankruptcy matters in the Second and Third Circuits, including a follow-up to the Supreme Court’s recent decision in Purdue, and Colleen has advised a variety of private sector clients on the potential impact of federal initiatives on their businesses.
Colleen has argued 11 cases before the Supreme Court, almost all of them in her prior role as an Assistant to the Solicitor General at DOJ. She was as an Assistant from 2019-2025, working on cases including 303 Creative v. Elenis, NetChoice v. Moody, and Seven County v. Eagle County.
She clerked for Chief Justice John Roberts and then-Judge Merrick Garland on the D.C. Circuit. Colleen graduated from Harvard Law School, and has a BA from Columbia, as well as a BA, MA, and PGCE from Clare College, Cambridge.
