Colin Powell said in a Sunday interview with CBS’ Face the Nation that the not guilty verdict in the trial of George Zimmerman for the shooting death of Trayvon Martin was “questionable,” and also said that GOP efforts at restricting voting rights would backfire.

“I think that it will be seen as a questionable judgment on the part of the judicial system down there,” Powell said of the Zimmerman verdict. “But I don’t know if it’ll have staying power. These cases come along and they blaze across the midnight sky and then, after a period of time, they’re forgotten.”

Powell, the country’s first black secretary of state and chairman of the joints chief of staff, spoke to host Bob Schieffer about how far the country has come from the days when he was refused a cheeseburger at a restaurant before the Civil Rights Act of 1964.

Civil Rights leaders and activists commemorated the 50th anniversary of the March on Washington, where Martin Luther King, Jr. delivered his “I Have a Dream” speech, Saturday at the National Mall. President Obama will deliver a speech at the Lincoln Memorial Wednesday.

Powell added that President Obama’s comments after the verdict, where he spoke about living as a black man in America, were an “accurate characterization of some of the things that we were exposed to,” and that he’d like to see Obama speak out more passionately about race.

“I used to refer to myself as the secretary of state who happens to be black, not the black secretary of state or black chairman—there ain’t a white one somewhere,” Powell said. “And so he [Obama] has a responsibility to the whole country, and I think he should speak out on these issues, not just because he’s the first black president, but because he’s the president of the United States and this is a problem that affects all of America, not just black America. It’s something that is still a residual effect of our history, of the racism that existed by law, of segregation and slavery and I think that we’re slowly, surely, moving away from this. It’s going to require more change in the hearts and minds of people, but, we’re going to get there, I have no doubt about that.”

On voting rights, Powell, who has publicly denounced North Carolina’s rollback, said the efforts to prevent minorities from voting will only backfire for Republicans.

“These kinds of procedures that are being put in place to slow the process down and make it likely that fewer Hispanics and African-Americans might vote, I think are going to backfire,” he said. “Because these people are going to come out and do what they have to do in order to vote, and I encourage that.”

Despite the challenges that he outlined, Powell said that, “we should be very proud of what we’ve accomplished.” Before adding that, in this day and age, King would march for jobs, economic opportunity, housing, and education.