WASHINGTON Kirstjen Nielsen defended her legacy of carrying out President Donald Trump s policy of separating migrant families as his homeland security secretary Tuesday, saying she was simply following the law.

I dont regret enforcing the law, said Nielsen at the Fortune Most Powerful Women Summit. The moderator, PBS journalist Amna Nawaz, repeatedly questioned Nielsen on whether she regretted signing off on a memo that authorized the routine separation of migrant children from their families so that their parents could be detained.

Nielsens appearance was wrapped in controversy. Activists had been pressuring Fortune to rescind its invitation to Trumps former homeland security secretary, who resigned in April. Three women who had been scheduled to speak at the summit filmmaker dream hampton , former secretary of state Hillary Clinton and singer Brandi Carlile withdrew from the event because of Nielsens participation.

Clifton Leaf, Fortunes editor-in-chief, acknowledged the controversy Tuesday in remarks introducing the session, saying that while he understood the criticism, part of Fortunes mission is to provide a platform for these discussions and he promised tough questions.

These issues are so important that we really need more voices. And we need to be additive and try to find a way to come together, and not work on taking people apart, Nielsen said, justifying why she deserved to be at the gathering.