Image credit: Mike Groll/AP Photo

New York state officials have passed a new law that they say should prevent the mentally ill from committing violent acts. The law was passed in the aftermath of the shootings at Sandy Hook Elementary School in Connecticut.

"We must stop the madness," Gov. Andrew Cuomo said, "and lead the way once again in saving lives."

The new law would require mental health professionals to report to state officials any patient they deem to be a "significant risk" or "threat."

Such reporting would block patients from buying weapons - no court order needed. The law might have made a difference in the mass shootings at Virginia Tech and at an Auroro, Colo., movie theater.

In both cases, the young men - Seung-Hui Cho and suspect James Holmes - reportedly received mental health counseling.

Dr. Paul Appelbaum and other experts though said they were deeply concerned that the law could destroy the trust patients place in therapists.

"This would be a sea change, " said Appelbaum, a leading scholar on psychiatry and the law. "It potentially opens up a huge number of patients to the intrusion of the state."

"I think the New York bill is unique in the degree of reporting that it would require and the intrusion in the therapist-patient relationship involved," he said.

The state's new law goes further than federal law, which bans gun purchases by people deemed by a court to be mentally ill. It also could lead to involuntary confinement.

"People who are concerned about their privacy may decide to not even come in to treatment in the first place," Appelbaum said. "People with mental illness account for a very small proportion of violence committed."

In a statement, the National Rifle Association called the law "draconian."

"While lawmakers could have taken a step toward strengthening mental health reporting and focusing on criminals, they opted for trampling the rights of law-abiding gun owners in New York…." the NRA said.

People who lost loved ones in recent shootings, though, said that something should have been much earlier about the access of the mentally ill to guns.

"Virginia Tech, Columbine, Aurora and Sandy Hook - they all have a common thread," said Lonnie Phillips, the father of an Aurora victim. "And it's all two parts. Mentally ill people with guns. … It's a lethal combination."

ABC News' Pierre Thomas, Jack Date and Jack Cloherty contributed to this article.