Here is the opinion in In the Matter of the Civil Confinement of Johnson.
The court’s syllabus:
The state does not have jurisdiction pursuant to Public Law 280 to civilly commit an enrolled member of a federally recognized Indian tribe as a sexually dangerous person under the Minnesota Commitment and Treatment Act. But in the absence of express congressional consent, the state does have jurisdiction to civilly commit an enrolled member of a federally recognized Indian tribe as a sexually dangerous person under the commitment and treatment act where, as here, federal law does not preempt state jurisdiction and exceptional circumstances exist.
Turtle Talk 
Assuming the tribal members involved in this case reside on-rez and such committment isn’t otherwise a condition of some state probation, I hope this gets appealed or a motion for reconsideration is filed.
Other things aside, via the Adam Walsh Act, the federal government has pervasively regulated the field. Pursuant to 42 USC 16927(a), the feds expressly granted the state of Minn. power to exercise civil regulatory authority over all sex offenders in Indian Country (except Red Lake). That grant of power is fairly broad and significant as it relates to public sex offender registries. Conspicuously absent from that grant is any authority to involuntarily commit sex offenders, despite the fact that the Act addresses the civil committment of sexually dangerous persons in Title 3.
I’m not sure how such a power grab by Minn. doesn’t conflict with federal policies on the matter. If the feds thought it was appropriate for states to exercise such authority over Indian Country they would have done so – they certainly had no problem expressly granting civil regulatory authority over the registry aspect of sex offender management.