It protects the public by taking dangerous offenders out of circulation.
Some think long jail terms keep the worst offenders out of circulation.
But Ms. Ahearn said that forcing sex offenders out into the open could actually help them deal with their problems.
New laws have enabled the department to move more nonviolent offenders out of correctional facilities and into their communities.
The law was intended to divert nonviolent drug offenders out of the prison system and into community treatment programs.
The Criminal Justice Agency, a private agency that has a contract to work with the courts, has helped judges find ways to keep offenders out of jail.
Eleven states, including Pennsylvania, Texas and Virginia, have passed laws that keep most young offenders out of adult jails and prisons.
By contrast, Grand Forks, N.D., about 85 miles away, has 13 sex offenders out of a population of 53,000 — a rate of about one in 4,000.
Private-probation companies, too, have quietly taken off in recent years, often selling themselves as a cheap way to keep small-time offenders out of jail.
Foremost among the bill's opponents is the provincial government in Quebec, which complains that the measure will undermine its successful efforts to keep young offenders out of jail.
Within seconds, dozens of officers and stewards had sprinted over to the Chelsea section, surrounded the fans, and bundled the offenders out.
