Bernstein served as Assistant Attorney General for Arizona from 1937 to 1939, and was a Delegate to the Democratic National Convention in 1940 and 1944.

He served as chairman of the Charter Review Committee that organized the charter government reform movement in Phoenix.On May 5, 1954, Bernstein ruled that segregation of African-American students in Phoenix's Wilson Elementary School District was a violation of the 14th Amendment in Heard vs. Davis.

On May 17, 1954, the Supreme Court announced its decision in Brown, that the doctrine of "separate, but equal" was unconstitutional.

[2] Bernstein was elected to the Supreme Court of Arizona in 1958, taking office the following January.

[2] In 1967, Bernstein and Governor Jack Williams, called a citizens' conference on Arizona courts, which resulted in a permanent organization called The Citizens' Association on Arizona Courts, "whose primary goal was the establishment of a system for the merit selection of judges."