United States v. Comstock:

In a broad endorsement of federal power, the Supreme Court on Monday ruled that Congress has the authority under the Constitution to allow the continued civil commitment of sex offenders after they have completed their criminal sentences.

The 7-to-2 decision touched off a heated debate among the justices on a question that has lately engaged the Tea Party movement and opponents of the new health care law: What limits does the Constitution impose on Congress’s power to legislate on matters not specifically delegated to it in Article I?

The federal law at issue in the case allows the government to continue to detain prisoners who had engaged in sexually violent conduct, suffered from mental illness and would have difficulty controlling themselves. If the government is able to prove all of this to a judge by “clear and convincing” evidence — a heightened standard, but short of “beyond a reasonable doubt” — it may hold such prisoners until they are no longer dangerous or a state assumes responsibility for them. http://www.nytimes.com/2010/05/18/us/politics/18offenders.html?_r=0

The Court has the power to detain:

Justice Stephen G. Breyer, writing for himself and four other justices, said the clause provided Congress with the needed authority as long as the statute in question was “rationally related to the implementation of a constitutionally enumerated power.”

Congress has the undoubted powers, Justice Breyer said, to enact criminal laws in furtherance of its enumerated powers and to create a prison system to punish people who violate those laws, though neither power is explicitly mentioned in the Constitution. “The civil commitment statute before us represents a modest addition,” he added, comparing it to medical quarantine.

Other states have enacted similar laws. In my state:

8. "Sexually dangerous individual" means an individual who is shown to have engaged in sexually predatory conduct and who has a congenital or acquired condition that is manifested by a sexual disorder, a personality disorder, or other mental disorder or dysfunction that makes that individual likely to engage in further acts of sexually predatory conduct which constitute a danger to the physical or mental health or safety of others. It is a rebuttable presumption that sexually predatory conduct creates a danger to the physical or mental health or safety of the victim of the conduct. For these purposes, mental retardation is not a sexual disorder, personality disorder, or other mental disorder or dysfunction.

9. "Sexually predatory conduct" means:
a. Engaging or attempting to engage in a sexual act or sexual contact with another individual, or causing or attempting to cause another individual to engage in a sexual act or sexual contact, if:
(1) The victim is compelled to submit by force or by threat of imminent death, serious bodily injury, or kidnapping directed toward the victim or any human being, or the victim is compelled to submit by any threat that would render an individual of reasonable firmness incapable of resisting;
(2) The victim's power to appraise or control the victim's conduct has been substantially impaired by the administration or employment, without the victim's knowledge, of intoxicants or other means for purposes of preventing resistance;
(3) The actor knows or should have known that the victim is unaware that a sexual act is being committed upon the victim;
(4) The victim is less than fifteen years old;
(5) The actor knows or should have known that the victim has a disability that substantially impairs the victim's understanding of the nature of the sexual act or contact;
(6) The victim is in official custody or detained in a treatment facility, health care facility, correctional facility, or other institution and is under the supervisory authority, disciplinary control, or care of the actor; or
(7) The victim is a minor and the actor is an adult; or
b. Engaging in or attempting to engage in sexual contact with another individual or causing or attempting to cause another individual to have sexual contact, if:
(1) The actor knows or should have known that the contact is offensive to the victim; or
(2) The victim is a minor, fifteen years of age or older, and the actor is the minor's parent, guardian, or is otherwise responsible for general supervision of the victim's welfare http://www.lawserver.com/law/state/n...ode_25_03-3_01

North Dakota Code 25-03.3-08 - Sexually dangerous individual - Procedure on petition - Detention

Current as of: 2009 Check for updates

1. Upon the filing of a petition pursuant to this chapter, the court shall determine whether to issue an order for detention of the respondent named in the petition. The petition may be heard ex parte. The court shall issue an order for detention if there is cause to believe that the respondent is a sexually dangerous individual. If the court issues an order for detention, the order must direct that the respondent be taken into custody and transferred to an appropriate treatment facility or local correctional facility to be held for subsequent hearing pursuant to this chapter. Under this section, the department of human services shall pay for any expense incurred in the detention or evaluation of the respondent.

2. If the state's attorney knows or believes the respondent named in the petition is an individual with mental retardation, the state's attorney shall notify the court in the petition and shall advise the court of the name of the legal guardian of the respondent or, if none is known, the court may appoint a guardian ad litem for the respondent. Before service of the notice required in section 25-03.3-10, the court shall appoint an attorney for the respondent. An individual with mental retardation may be detained in a correctional facility before the probable cause hearing only when no other secure facility is accessible, and then only under close supervision. http://www.lawserver.com/law/state/n...ode_25_03-3_08

And so it is, a person may be "punished" for what he/she might do.