In one sense, the relationship Roberta Kaplan had with pro bono client Edith Windsor was no different than the relationships she has had with her corporate clients at Paul, Weiss, Rifkind, Wharton & Garrison.

“I have this ability—or deficiency, depending on how you look at it—to convince myself that whoever my client is, they've done absolutely nothing wrong, that they're totally right,” said Kaplan, a partner at the firm for nearly 17 years.

But in every other sense, Windsor became a client like no other, a client whose case led Kaplan to the U.S. Supreme Court, where she argued successfully to overturn the Defense of Marriage Act, allowing Windsor to escape estate taxes after the death of her spouse and partner of more than 40 years, Thea Spyer.