The U.S. Supreme Court has declined to hear a case challenging the constitutionality of Minnesota's treatment system for sex offenders, another setback to a long-standing series of efforts to reform the program.

The Minnesota Sex Offender Program (MSOP), which confines about 720 offenders at secure treatment centers in Moose Lake and St. Peter, has been the target of repeated legal challenges for its practice of confining offenders indefinitely after they have already completed their prison terms.

Civil rights attorneys and some state legislators have been pushing for changes that would put offenders on a faster path toward release.

A class of sex offenders sued the state in 2011, arguing during a six-week trial that Minnesota's system violated their due-process rights under the U.S. Constitution by depriving them of access to the courts and other basic safeguards found in the criminal justice system.

In June 2015, U.S. District Judge Donovan Frank in St. Paul declared the MSOP unconstitutional, citing the program's low rate of release and lack of regular risk evaluations of offenders. But after reviewing the program, a three-judge panel of the Eighth U.S. Circuit Court of Appeals in St. Louis concluded earlier this year that Minnesota provided adequate constitutional protections, including the right to petition for release.

The U.S. Supreme Court decision not to hear the case, announced Monday morning, effectively upholds the appellate panel's decision.

Dan Gustafson, the lead attorney for the class of sex offenders who sued over the program, expressed disappointment Monday that justices wouldn't review an appellate opinion that he said "essentially removes the possibility of federal court review of state action dealing with fundamental rights."

Gustafson said that remaining challenges to the MSOP now are limited to state court litigation or changes imposed by the Legislature. For now, however, he said his clients "continue to face the prospect of lifetime commitment at MSOP that admittedly fails to safeguard their rights."

The Supreme Court's decision "should concern everyone who believes that the federal courts should jealously guard the constitutional rights of groups of unpopular citizens threatened by popular political decisions," Gustafson said in a statement.

"Without federal court intervention, issues such as a woman's right to choose, access to higher education and school desegregation, the protection of voting rights, immigration rights, and the right for all citizens to marry could not have been achieved."

Gov. Mark Dayton, in a statement Monday, pushed for a legislative solution to MSOP reform. Dayton proposed $18.4 million last session in new funding for "facilities improvements" and staffing.

"Importantly, this ruling does not mean that we abandon our ongoing reforms, to prioritize the safety and well-being of all Minnesotans," Dayton said. "Rather, this ruling will allow us to continue the reforms we have begun, rather than operate under a federal directive."

To date, just one offender has been fully discharged from the MSOP in its more than 20-year history, while 15 have been conditionally discharged. Of those, eight are now living in the community. As of Friday, 89 people were living in a private residence on the St. Peter campus that is outside of the secure facility. An additional 21 offenders are waiting for beds to open there, according to the state.

Eric Janus, a professor at the Mitchell Hamline School of Law in St. Paul and author of a book on sex offender commitment laws, also pointed to the state courts for the possible next challenge to the MSOP, citing the roughly 80 community residency restrictions across Minnesota that could hold up the placement of some sex offenders scheduled for release.

But on Monday, Emily Piper, commissioner of the Minnesota Department of Human Services, struck a triumphant tone, describing the Supreme Court's decision as validating, "given the criticism the Minnesota Sex Offender Program has faced."

"I have always believed this program is constitutional and important for public safety in Minnesota," Piper said. "I am proud of our program staff who have weathered criticism and continued to serve the people of Minnesota in the face of the uncertainty created by this litigation."

Stephen Montemayor • 612-673-1755

Twitter: @smontemayor

Chris Serres • 612-673-4308

Twitter: @chrisserres