Holder spoke at a conference on child sexual abuse in Washington.
From his prepared remarks:
It is fully possible to permit law enforcement to do its job while still adequately protecting personal privacy.
When a child is in danger, law enforcement needs to be able to take every legally available step to quickly find and protect the child and to stop those that abuse children.
"It is worrisome," he said, "to see companies thwarting our ability to do so."
He didn't mention Apple or Google by name, but that's certainly the context, given that both companies in September announced new mobile phone encryption policies that sparked a number of protests from government officials.
With the latest iteration of its mobile operating system, iOS 8, Apple said it was no longer holding encryption keys and wouldn't be able to turn iPhone or iPad data over to cops anymore.
Likewise, the next generation of Google's Android operating system, due for release this month, will for the first time encrypt data by default, thus putting up yet another roadblock to stop police from getting at the troves of personal data we all keep on our mobile gadgets.
Normal people who are sick and tired of surveillance were cheered by these moves.
Police were not, and Holder's not the first one to get vocal about it.
Ronald T. Hosko, former Assistant Director of the FBI Criminal Investigative Division, published an opinion piece in The Washington Post last week about how Apple's move will hamstring the law.
Hosko said that while Apple's move didn't make it any harder to tap or legally intercept calls with a warrant, it does "limit law enforcement's access to... data, contacts, photos and email stored on the phone itself."
Well, yes, it does make it harder, but it by no means makes it impossible.
iOS forensics expert Jonathan Zdziarski, who's actually trained police on how to get data off of iPhones, a few weeks ago put up a post outlining how not-hard it is, given how very not-infallible iOS 8 is to intruders - particularly government-funded ones.