An ongoing “sweep” led by the U.S. Marshals Service to track down convicted sex offenders who have failed to update their addresses with local police is one more example of how difficult it is for society to deal with this crime.

No one convicted of any other felony, including murder, is treated the same way, and yet the tracking of released sex offenders remains an expensive and questionable technique for safeguarding citizens from the danger they may continue to present.

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Members of the U.S. Marshals Service, Portland Police Department and Cumberland County Sheriff's Office made visits to registered sex offenders in Portland on Friday to conduct checks as a part of a nationwide effort to crack down of non-compliance. Such efforts cannot be a solution to the problem of recidivism. Derek Davis/Staff Photographer

Under a 2006 federal law, the Adam Walsh Act, named for a boy kidnapped and murdered by a sex offender, the marshals are the lead agency overseeing compliance with the requirement that sex offenders register with local law enforcement.

Any new address requires updating, and this sweep, called “Operation Guardian,” involved federal, state county and local authorities tracking down offenders and trying to find those with incorrect addresses or who had failed to file any location data.

The sweep was timed to coordinate with the opening of school, since the law mandates that offenders live a certain distance away from schools, day care centers, playgrounds and other locations where children gather.

As of the end of last week, nearly two dozen offenders had been arrested for noncompliance with the law, and the effort is expected to continue across the state for several more weeks.

The effort, as necessary as it is, however, cannot be a solution to the problem of recidivism. The rationale for the sweep is that people who have a record of such crimes are highly likely to commit them over and over again, and such treatments as they receive have been ineffective in many cases.

Second, requiring an offender to live a given distance away from a given location offers no guarantee whatsoever that such a person can’t still walk or drive there, even if they are legally prohibited from doing so. After all, child sexual abuse is a worse crime than violating standards of release, and if an offender is willing to do that, a mere travel ban is minuscule.

Sadly, the only way to keep hard-core sex offenders harmless is to keep them where not only is their address known, they also can’t refuse to provide it: prison. That is, longer sentences and no chance of their reduction is the only strategy guaranteed to work.