That is because in the USA, the people grant the federal government it's powers; the federal government doesn't decide what those powers will be. At least in theory. So our government doesn't limit it's own powers, we do, usually by way of the courts. And when any part of that federal government grossly oversteps the powers we've granted it, some of us get quite upset about it.

Well, it's not exactly clear what powers we the people have granted the Federal Government, so the courts (part of the government) exist partially to interpret that. In this case, which should be cause for celebration, the courts came to the conclusion (which I think most here would agree with) that those powers do not include pulling cell phone records at will.

The commenter to which I responded got off topic on an anti-government tangent that made a number of assumptions not at all related to the article for no other reason than to make an anti-government rant, which I grant is a cheap source of karma here.

You have a constitution that is designed to prevent one man at the head of one agency deciding he doesn't like blacks, or communists or Jews or Muslims.

Instead you need at least the supreme court to decide you don't like these people. If you are allowed to tell phone companies to break the law and you will pardon them later - where do you stop?