Among the several big decisions delivered today, including apartial overturning of Arizona’s SB 1070and adefense of Citizens United, the Supreme Court ruled, 5-4, that mandatory life sentences without parole for juveniles convicted of murder violate the Eighth Amendment.

“By requiring that all children convicted of homicide receive lifetime incarceration without possibility of parole, regardless of their age and age-related characteristics and the nature of their crimes, the mandatory sentencing schemes before us violate this principle of proportionality, and so the Eighth Amendment’s ban on cruel and unusual punishment,” Justice Elena Kagan wrote in the majority opinion. Kagan was joined by Justice Ruth Bader Ginsburg, Justice Stephen Breyer, Justice Sonya Sotomayor, and Justice Anthony Kennedy.

The decision inspired three separate dissenting opinions, from Chief Justice John Roberts, Justice Clarence Thomas, and Justice Samuel Alito, who felt strongly enough that he read a portion of his opinion from the bench.

“Even a 17½-year-old who sets off a bomb in a crowded mall or guns down a dozen students and teachers is a ‘child’ and must be given a chance to persuade a judge to permit his release into society,” Alito wrote. “Nothing in the Constitution supports this arrogation of legislative authority.”

Alito argued that the majority decision shows that Eighth Amendment cases are “no longer tied to any objective indicia of society’s standards.”

“Future cases may extrapolate from today’s holding, and this process may continue until the majority brings sentencing practices into line with whatever the majority views as truly evolved standards of decency,” he wrote.

Please note that Alito seems to ignore — deliberately, I hope, because the alternative is that he’s stupid — that this is just about mandatory sentencing. The majority did not rule that juveniles can not be subjected to life in prison, just that it could not be mandatory. You know, due process and the right of the accused to defend himself and all that. You know that Constitution that Alito seems to think gives lots of rights to corporations?

A judge and/or jury can still decide that “ a 17½-year-old who sets off a bomb in a crowded mall or guns down a dozen students and teachers is a ‘child’” who is mature enough to understand the consequences of his or her actions and be sentenced accordingly.

It is profoundly disturbing to me that Alito — or any Supreme Court Justice — seems to think that judges shouldn’t be given any leeway in the application of the law or sentencing, and seeks to shackle them to mandatory sentencing guidelines set up by politicians, not legal scholars.

The Roberts Court is the very definition of Activist Court. This is frightening to me, because they’re just getting started. The court may not tip back to sanity in my lifetime.