The state Legislature must decide in its upcoming session whether to enact laws that would bring the state into compliance with a federal sex offender act that puts adolescent sex offenders as young as 14 in a national public registry.

The state Senate majority leader, Dean Skelos, intends to comply with the Adam Walsh Child Protection and Safety Act of 2006, a spokesman, Scott Reif, said. It is not clear, however, whether the Assembly will agree to pass the necessary legislation.

Supporters call the Walsh Act a tool to improve monitoring and toughen punishment of sex criminals, while opponents say the law stigmatizes juveniles, does not take risk assessments into account, and would be too costly to implement.

“This is a difficult one, and it’s going to take a careful look to see whether or not we are going to do this,” Assemblyman Joseph Lentol, a Democrat of Brooklyn who is chairman of the Assembly Committee on Codes, said.

States have until July 2009 to comply with the act or risk losing 10% of the federal money, known as Byrne grants, used for enforcement purposes, according to the Division of Criminal Justice Services. New York State stands to lose about $800,000.

The act, signed by President Bush in July 2006, requires states to submit information on sex offenders to a national public registry; imposes mandatory minimum penalties for the most serious offenses; and mandates civil confinement for sex offenders who are deemed too dangerous to be released from prison.

The federal government enacted the legislation to ensure that states register sex offenders in a uniform fashion and that offenders who do not register are penalized, the founder of Parents for Megan’s Law and the Crime Victims’ Center in New York, Laura Ahearn, said. About 100,000 sex offenders are missing nationwide, she said.

Her group’s research found that “where you lived determined how well you could protect yourself or your children from known convicted sex offenders,” Ms. Ahearn, who helped draft the Adam Walsh Act, said.

New York State would have to make significant changes to comply with the federal bill, a spokesman for the Division of Criminal Justice Services, John Caher, said. “This is such an enormous sea change and there are so many considerations to take into account. If we were to deal with, it would take a great deal of effort,” he said.

The state already has a sex offender registry, which it has used for the last 12 years and which lists more than 27,000 offenders, he said. But to comply with the act, New York would have to drop its risk assessment process, which enables the state to determine how long an offender should have to register based on his or her determined threat to society, and to implement a procedure of setting registry requirements based on conviction, the director of the Division of Criminal Justice Services’s Office of Sex Offender Management, Luke Martland, said.

New York State also would have to include more people in its registry and add juveniles who have been adjudicated in juvenile court of an offense comparable to or more severe than aggravated sexual abuse, Mr. Martland said. Currently, the records of most juvenile sex offenders in New York are sealed and juveniles are not put in public registries, he said.

“Common sense would tell you that having your name, picture, and home address on the Internet as a sex offender at age 8, 12, or even 14 could be devastating in terms of peer relationships, community [relations], ability to stay in school, and involvement in church activities,” a co-director of the Adolescent Sex Offender Treatment Program at the University of Oklahoma Health Sciences Center, Barbara Bonner, said.

“We are talking about people, who are juveniles or adults, who are raping little kids,” a child advocate, Marc Klass, whose daughter Polly was raped and killed in 1993, said. “The public should know who this highly recidivist individual is so they could use this information to protect themselves.”