Though few Americans know it, the exception clause in the 13th Amendment makes a person a slave when they are convicted of a crime and sent to prison. I know that former President Barack Obama, a constitutional scholar and a Black man, understands this. I applaud his efforts to address issues of mass incarceration. I understand the symbolism of his visit to a federal prison, the only American president to ever do so. These were important first steps, but there is a long road ahead.