Kaplan served as a
law clerk for
Mark L. Wolf of the
U.S. District Court in Massachusetts. While clerking for
Judith Kaye, of the
New York Court of Appeals, she assisted Kaye with a number of academic articles. Kaplan's scholarly articles include "Proof versus Prejudice" (2013). Kaplan joined the law firm
Paul, Weiss, Rifkind, Wharton & Garrison LLP in 1992 and made partner in 1999. She has served on the board and as chair of the board of the
Gay Men's Health Crisis, which created the Roberta Kaplan Legal Center to provide free legal services.
United States v. Windsor In 2009, Kaplan agreed to represent
Edith Windsor pro bono. Windsor's wife, Thea Spyer, had died two years after they wed in Canada, leaving Windsor her sole heir. Because their marriage was not recognized under existing U. S. federal law, Windsor received an estate tax bill of $363,053. Windsor went to gay rights advocates seeking redress, but could find no one to take her case. She was referred to Kaplan, who later recalled, "When I heard her story, it took me about five seconds, maybe less, to agree to represent her." Kaplan had been co-counsel on the unsuccessful bid for marriage equality in New York state in 2006. On June 26, 2013, the U.S. Supreme Court issued a 5–4 decision declaring Section 3 of the Defense of Marriage Act to be unconstitutional. Subsequent to
Windsor, the Supreme Court ruling in
Obergefell v. Hodges (2015) struck down all remaining state and federal laws against same-sex marriage across the United States. Kaplan wrote about
United States v. Windsor in the book
Then Comes Marriage.
Sines v. Kessler In 2017, Kaplan and co-counsel
Karen Dunn filed a civil lawsuit on behalf of students, clergy members and local residents against 15 individual defendants and associated groups for damages following alleged injuries sustained at the 2017
Unite the Right rally in
Charlottesville, Virginia. In 2019, Kaplan and Tchen later co-founded HABIT, an anti-sexual harassment advisory. and after an open letter from a group of former Time's Up staffers and clients to the board of Time's Up was published. The report alleged Kaplan was involved in an effort to discredit a woman who had accused Cuomo of sexual harassment. The lawsuit was moved from state to federal court when the US Department of Justice moved to take over Trump's defense (a motion that was denied in October 2020). Kaplan said she welcomed pursuing the lawsuit in federal court. Kaplan represented Carroll in her civil trial
E. Jean Carroll vs. Donald J. Trump, that began on April 25, 2023, in federal court at the
United States District Court for the Southern District of New York. The jury found in favor of Carroll on May 9, 2023, and awarded her damages of $5 million after finding Trump liable for sexual abuse and
defamation. On January 26, 2024, after a second defamation trial against Donald Trump that was limited only to the question of damages for statements Trump made while president, a different jury awarded Carroll $83.3 million in compensatory and punitive damages.
Mary Trump v. Donald Trump et al. On September 24, 2020, Kaplan and her firm filed a lawsuit with the
New York Supreme Court in Manhattan, on behalf of plaintiff
Mary L. Trump, accusing President
Donald Trump and his siblings,
Maryanne Trump Barry and
Robert Trump, of decades of financial fraud and civil conspiracy. ==Works==