The association took down the site after it was hacked late Friday afternoon by people claiming to be linked to the group Anonymous, association spokesman Joe Couto said.
The identity of those responsible for the attack has not been confirmed, but activists allied to the loose-knit Anonymous movement had threatened to target federal Public Safety Minister Vic Toews and others over the Harper government's surveillance bill.
The chiefs had supported the legislation.
"What this does is demonstrate quite clearly to Canadians the type of cyber crimes perpetuated every day," Couto said Saturday.
"The citizens of this province and this country are asking us to address cyber crimes and we need tools for that," he said.
He said police are currently bound by laws drafted in the 1970s, "when the rotary phone was cutting-edge technology."
Couto said the hackers posted login information for senior members of the association on the website. The organization replaced it with a terse message that read," Under Maintenance."
Ontario provincial police are investigating the breach to determine how much information was accessed, Couto said.
While the organization doesn't keep sensitive information about court cases, it does have databases on senior police officers, he said.
Meanwhile, the Mounties said earlier this week that they had not yet decided whether to launch a full investigation into the threats made against Toews.
Part of the online campaign against Bill C-30 involved the publication of the minister's divorce records, while other people are mocking the bill's supposed powers by sending the minister mundane details of their lives.
Among other things, the bill gives authorities access to Internet subscriber information without requiring a warrant and there are concerns that it violates the privacy of Internet users.
Saturday's hacking came a day after Anonymous claimed responsibility for vandalizing an Ohio FBI partner website, replacing its homepage with the video for rap hit "Gangsta's Paradise."
The group, a collection of activists and Internet mischief-makers, has increasingly focused its energy on military, police and security companies in recent months.
Among its most spectacular coups: The interception of a conference call between the FBI and London police cyber-investigators working to track them down.
At least one element within the group has promised weekly attacks on government-linked targets.
_ With files from The Associated Press.
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