My understanding is that you can take away firearms from people who do not have mental health issues, but in cases where you have received reports of spousal violence, or about a depressed young person who makes the decision to go in a school with a firearm and shoot at all the kids. If a school notifies you about such a comment, you are going to check and remove the firearms as a preventive measure. You are not necessarily removing the firearms from criminals. It can also be anyone in the street.
On May 4th, 2010. See this statement in context.