James M. Nabrit argued several civil rights cases before the U.S. Supreme Court and was a longtime lawyer for the NAACP Legal Defense and Educational Fund. (Courtesy of NAACP Legal Defense and Educational Fund)

James M. Nabrit III, a civil rights lawyer who argued several prominent cases involving education and free speech before the U.S. Supreme Court from the 1960s to the 1980s, died March 22 at Suburban Hospital in Bethesda. He was 80.

He had lung cancer, said Elaine Jones, a former president of the NAACP Legal Defense and Educational Fund, where Mr. Nabrit worked for 30 years.

Mr. Nabrit (pronounced NAY-brit), whose father was a leading civil rights lawyer who also served as president of Howard University, argued a dozen cases before the Supreme Court on such fundamental issues as education, free speech and access to public accommodations.

His most noteworthy case may have been Keyes v. School District No. 1, Denver (1973). It was the first school desegregation case to reach the Supreme Court from a state that did not have segregation laws.

The Supreme Court agreed with Mr. Nabrit’s argument that de facto segregation in Denver left minority students with inferior facilities and staff members, thus denying the students equal opportunity to a good education.

“He really was one of the greatest lawyers in the civil rights movement,” Ted Shaw, a former president and director counsel of the Legal Defense Fund, said Tuesday in an interview. “Jim was part of the backbone of the legal team that defended civil rights and was partly responsible for bringing civil rights law out of the darkness. He had a profound effect on the law.”

In 1959, Mr. Nabrit was hired at the Legal Defense Fund by Thurgood Marshall, who in 1967 became the first African American justice on the U.S. Supreme Court. Nabrit recalled working on cases with Marshall in Louisiana with a guard stationed outside their room at night bearing a shotgun.

Mr. Nabrit handled several sit-in cases in which African American college students were denied service at restaurants and other public accommodations in the 1960s. He worked on school-discrimination cases in Virginia, North Carolina, Arkansas and Louisiana, as well as death-penalty cases in Alabama, Florida and other states.

“The Supreme Court was ahead of the other branches of government in opposing discrimination,” Mr. Nabrit said in 2001 interview with Washington Lawyer magazine. “President Eisenhower and President Kennedy both supported some aspects of civil rights legislation, but the Court was the leading institution.”

In 1965, Mr. Nabrit and LDF President Jack Greenberg drew up a plan that was approved by a federal judge allowing the Selma-to-Montgomery march, led by the Rev. Martin Luther King Jr., to go ahead.

Mr. Nabrit worked on the Supreme Court appeal of a case from Birmingham, Ala., in 1963 in which King and other marchers were jailed after they were denied permission to stage a march. While incarcerated, King wrote his celebrated “Letter From Birmingham Jail.”

In 1969, Mr. Nabrit won a unanimous Supreme Court decision after civil rights leader Fred Shuttlesworth, who died in 2011, was denied a parade permit in Birmingham, in violation of his right to free speech.

“There are a lot of people who are heroes whose names are well known,” Jones, who was president of the Legal Defense Fund from 1993 to 2004, said Tuesday. “Jim Nabrit is one of those unsung heroes whose names were not known. The heroes we know of depended on his advice.”

James Madison Nabrit III was born June 11, 1932, in Houston. He grew up mostly in Washington and recalled seeing Marshall, William H. Hastie and other civil rights lawyers at his family’s dinner table.

His father, James M. Nabrit Jr., developed the country’s first course in civil rights law at Howard in the 1930s and was one of the principal architects of the legal strategy behind Brown v. Board of Education, the landmark 1954 case in which the Supreme Court overturned segregation in public schools.

Mr. Nabrit’s father was Howard University president from 1960 to 1969, with a hiatus from 1965 to 1967, when he was U.S. ambassador to the United Nations.

The younger Mr. Nabrit attended Dunbar High School and graduated from what is now the Northfield Mount Hermon School, a private boarding school in Massachusetts. He graduated from Bates College in Lewiston, Maine, in 1952 and from Yale Law School in 1955. He served in the Army and practiced at the Washington firm Reeves, Robinson & Duncan before joining the Legal Defense Fund.

After retiring in 1989, Mr. Nabrit moved to Leisure World in Silver Spring. His wife of 52 years, the former Roberta Jacquelyn Harlan, died in 2008. He had no immediate survivors.

His interests outside the law included photography, computers, scuba diving and performing magic.

Mr. Nabrit served on the LDF board for many years and advised on many legal cases, including one on the current docket of the Supreme Court.

“If there were such a thing as civil rights royalty,” Shaw said, “Jim would be a prince.”