This is exactly what I (and the article) meant as well. Likewise Udall and Wyden.
That is, when the court creates new interpretations of existing laws (and the Constitution itself, as in the example), then it is effectively creating new laws. Of course, these are not laws in the sense that Congress passes them. Instead, these become "precedent" to the extent that future rulings can rely upon them.
Now, such interpretation is a "normal" thing that is done out in the open with, for example, The Supreme Court. Of course, there are two (adversarial) parties when this happens.
But, when this (secret) court is carving out these new interpretations of Constitutional law based solely on the assertions of the government (i.e. without adversarial debate), then we have a very big problem.
So, I would also be interested in hearing why the parent doesn't find Wyden's and Udall's complaints compelling.
2. I suppose I'm speaking of "The Law" in general terms, in that I don't imagine that FISC takes a red pencil to particular sections of the United States Code. However, "code" is a bit of a misnomer, because it's never "compiled". Instead, relevant terms that govern e.g. what circumstances justify a particular finding are interpreted in mostly consistent ways. The law effectively changes when those interpretations change. As a more specific example of this, I think Senators Udall and Wyden have been pretty clear in their accusations, at least recently. If you don't find their complaints compelling, why not?