As someone who reads a lot of undergraduate writing, I’m all in favor of mandatory sentences. Also, mandatory knowing the differences between the possessive and the plural. Still, that’s not what most people mean.
What most people mean by “mandatory sentences” is an artifact of the violent and politically-polarized 1970s. Plagued with violence and the early stages of the now-failed “war on drugs,” Americans supported the passage of laws that took sentencing out of the hands of “bleeding heart liberal” judges. The first of these appeared in liberal Republican Nelson Rockefeller’s 1973 drug laws in New York state. Although the laws were passed as a response to a heroin epidemic, anyone arrested in possession of 4 ounces of “narcotics” got 15 years in prison. Other states followed suit, but the federal government held back. Then, in 1982, Boston Celtics first-round pick Len Bias dropped dead of a coke overdose before he could play a single game. House Speaker Thomas P. “Tip” O’Neill (D-Massachusetts) immediately pushed for and won a new federal law that mandated at least five years imprisonment for anyone found in possession of 5 grams of “crack” cocaine. Anyone convicted of involvement in a “continuing criminal enterprise” (i.e. a drug gang) caught a 20 year bit.
As a result, from the 1970s to today, America has gone from having 600,000 people in prison to having 2.4 million people in prison. This is, purportedly, the highest per-capita imprisonment rate in the world. Of those 2.4 million people in prison, 1.3 million are there for non-violent, drug-related crimes. This costs taxpayers a lot of money: $80 billion a year.
The thing is, most (50+ percent) of the people involved in the drug trade are black. Really? Well, not necessarily. Blacks are four times as likely as are whites to be arrested for possession of marijuana, and they usually catch a 20 percent longer sentence than do whites for the same charge. That leaves the whole issue of white boys who deal drugs, but don’t get caught, or who get caught and are allowed to plead down. Not that this happens in every case.
How does imprisonment affect political participation? About 7.7 percent of the adult African-American population is barred from voting because of having been convicted of a felony. If African-Americans constitute about 13.0-14.0 percent of the population, then the dis-franchised probably constitute about 1 percent of total potential voters. That could be enough to swing a tight election.
 “Rethinking mandatory sentencing,” The Week, 20 September 2013, p. 11.
 The Boston Globe lobbied for Boston to be granted a supplemental draft pick because Bias had never been able to play for the Celtics. The NBA wasn’t having it.
 See: Governor Earl Warren and Japanese internment.
 “Noted,” The Week, 18 October 2013, p. 16.