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.