The rationale behind mandatory sentencing is that it keeps punishment uniform. But it only seems to do so. It simply transfers discretion from the judge to the prosecutor, who exercises it by choosing which charges to bring or whether to bring any at all. Prosecutors use the draconian sentences as a club to extract plea bargains.

The system allows U.S. attorneys to dish out leniency in exchange for cooperation. Thus, suspects with much information to trade can get light sentences. One consequence is that drug ringleaders have gotten much shorter sentences than defendants only tangentially connected to the ring, such as a leader's girlfriend, since the latter has little information to swap. Giving the judge discretion can prevent such injustices.

The Journal Sentinel echos a point TalkLeft recently rcently made: there's no need for change.

Judges are by and large heeding the guidelines. Yet they retain the ability to depart from them in the interest of justice. Congress mustn't take that flexibility away again.