Flaum was in private practice in Chicago, Illinois from 1964 to 1965. He then transitioned into public service as an Assistant State's Attorney of Cook County, Illinois, from 1965 to 1969. He served as a Lecturer, Northwestern University School of Law from 1967 to 1969, and he helped found the Police Legal Advisory Program at Northwestern. Flaum was an Assistant Attorney General of Illinois from 1969 to 1970, and he became First Assistant Attorney General of Illinois from 1970 to 1972. He was First Assistant United States Attorney for the Northern District of Illinois from 1972 to 1975.[1]
In March 2017, Flaum found that police officers could not be sued for needlessly destroying property during a search because they had prevented the owner from witnessing which officers had caused the damage.[2] Judge David Hamilton partially dissented, arguing that the owner should not have been required to instead plead a novel "conspiracy of silence" claim.[3]
On April 4, 2017, Flaum wrote a concurrence when the 7th Circuit upheld (in an 8–3 vote) that employment discrimination based on sexual orientation violates Title VII of the Civil Rights Act.
Flaum wrote:
"Consequently, employment discrimination based on an employee’s interracial relationship is, in part, tied to an enumerated trait: the employee’s race. This type of discrimination is prohibited by Title VII.
The same principle applies here. Ivy Tech allegedly refused to promote Professor Hively because she was homosexual—or (A) a woman who is (B) sexually attracted to women. Thus, the College allegedly discriminated against Professor Hively, at least in part, because of her sex. I conclude that Title VII, as its text provides, does not allow this."
Flaum was joined by Kenneth Francis Ripple in his concurrence, and the two of them joined part of the majority opinion written by Diane Wood.[4]
On April 19, 2018, Flaum was the deciding vote in blocking Indiana's fetal burial requirement. Flaum was also in the 3–0 majority to block Indiana's ban on abortions due to race, sex, or disability. The majority opinion was written by William J. Bauer, and the 2–1 and 3–0 discrepancy comes from the partial dissent of Daniel Anthony Manion.[5]
On June 25, 2018, Flaum again cast the decisive vote in favor of abortion rights, to deny rehearing of the April 2018 cases.[6] The U.S. Supreme Court partially overturned and partially declined to review the opinion in Box v. Planned Parenthood of Indiana and Kentucky, Inc.
Despite his 2018 votes in favor of abortion rights, on November 1, 2019, Flaum voted to rehear a case after a three-judge panel blocked Indiana's parental notification requirements. Flaum joined a dissent written by Michael Stephen Kanne.[7]
On September 7, 2018, Flaum ruled that the felon dispossession statutes that barred felons from getting rifles does not violate the Second Amendment. Flaum was joined by Kenneth Francis Ripple over the dissent of Amy Coney Barrett.[8]
