Northwestern University said Ruder died Saturday at age 90.
Ruder led NU's School of Law from 1977 to 1985, and continued to teach there until 2017. He also served as chairman of the U.S. Securities and Exchange Commission during the late '80's.
Ruder was regarded as a leading scholar in corporate and securities law, teaching courses on insider trading, tender offers and other regulatory subjects, the school said.
"David took such delight and pride in the Law School," said Kimberly Yuracko, dean of Northwestern Pritzker Law. "For me personally, he was a dear friend, mentor and advisor. David welcomed me with warmth and kindness when I joined our faculty and was always generous with his time, wisdom and support."
A funeral will be held at Kelley & Spalding Funeral Home in Highland Park on February 22, from 1-5 p.m. Northwestern plans to hold a memorial service at the Law School April 18 from 2-3:30 p.m.