Never knew this, but apparently many federal agencies are self funding, in other words, they don't need Congress to appropriate money so that they can operate. This would seem to put them well above any Constitutional oversight. Although Congress could pass legislation to reign them in, it is much harder to pass specific legislation than it would be to change funding levels for an unnecessary or wasteful program. It is these kinds of stories that remind me how out of control the federal government has become.
Here's more from Michael Greve: