The Supreme Court's ruling this week that California's prisons are so overcrowded it amounts to cruel and unusual punishment -- requiring the release of 30,000 prisoners -- is rightly being heralded as a landmark case for the rights of the incarcerated.

But it's also the latest in a decade-long backlash against the lock-'em-up approach to criminal justice that took off during the 1980s and 1990s, leading to a grim situation in which the U.S. had only five percent of the world's population, but 25 percent of its prisoners.

The nation's skyrocketing incarceration rate not only exacerbated racial inequality and had counter-productive results in communities; it was also expensive. Because more than 90 percent of prisoners are under state custody, in 2008 states found themselves spending $52 billion a year on corrections -- a big number in good times, and an unsustainable sum during a time of recession and record budget shortfalls.

That need to save money -- not legal or humanitarian concerns -- spurred a national movement, led by state lawmakers, to reverse over two decades of zealous prison-building, draconian sentencing and swelling inmate populations.

Many of these state leaders for criminal justice reform have come from Southern states, which has long led the country in its incarcerate rate. Here's how Southern states stack up against California in terms of their incarceration rate per 100,000 population, according to the latest figures from The Sentencing Project:

PRISON POPULATION PER 100,000 RESIDENTS
Louisiana: 881
Mississippi: 702
Alabama: 650
Texas: 648
Florida: 559
Georgia: 526
Arkansas: 522
South Carolina: 512
National: 502
Virginia: 480
Kentucky: 478
California: 457
Tennessee: 426
North Carolina: 369
West Virginia: 346

These numbers are why lawmakers like Rep. Jerry Madden, a Republican state legislator in Texas, have led the push for reform. A 2007 projection showed that Texas would need to spend $1.6 billion by 2012 just to build new prisons to handle the flood of new inmates.

That led Madden to champion legislation that was less focused on punishment, and more on prevention and rehabilitation. As NPR reports:

At the Texas State House, Madden focused on diverting low-level drug abusers and mentally ill convicts into intensive, community-based treatment programs. He aimed at building halfway houses and treatment centers instead of prisons. And he pushed for increased supervision of inmates upon release.

And because the effort was led by a Republican, Madden was able to pass it in the legislature. The result? According to NPR: "Texas built no new prisons. It saved money. The crime rate dropped. And so too did the number of inmates committing crimes when they got out."

The Supreme Court's decision on California prisons only increases the incentive for states to abandon the costly push to incarcerate and pursue more effective, inexpensive and humane alternatives.