Supreme Court Justice Sonia Sotomayor says Justice Anthony Kennedy was passionate about the Constitution and the court.
"It is undeniable that he has had a monumental effect on the law," she said in a statement.
She continued: "I have witnessed his love and dedication to his family and know that he will cherish spending more time with them. I will miss working with him dearly, but I know he will continue to be a roaring lion, even as he takes senior status."
Justice Elena Kagan also weighed in on Kennedy's retirement.
"His legacy will be of enduring importance," Kagan said. "The Court and country will miss his wisdom, his independence and integrity, his love of liberty and commitment to personal dignity.