I'm confused as to why the DOJ is arguing over whether it needs a warrant or not for emails and Facebook chats and that sort of thing. This is the DOJ that we'r

I'm confused as to why the DOJ is arguing over whether it needs a warrant or not for emails and Facebook chats and that sort of thing. This is the DOJ that we're talking about, and surely, even if a warrant is required for email, they would be able to get that warrant regardless. A warrant is simply a permission by a judge to obtain or enter certain private property, right? Wouldn't the DOJ be able to find a judge that will grant a warrant? I don't know anything about judicial law, so I'm interested in learning about how this all works.