We also know that this Parallel Construction process really does happen. Thomas Tamm, https://en.wikipedia.org/wiki/Thomas_Tamm/, one of the many pre-Snowden leakers, was a lawyer at the Justice Department whose job it was to prepare warrants for the FISA court. He had cases where the basis for the warrant, the "probable cause", was based on illegal warrentless surveillance by the NSA. He knew that this was illegal but it was up to the FISA court to deny the warrants. They didn't. Instead they granted many such warrants and the decisions were never open to public scrutiny. After seeing too much of this, Tamm leaked the story to the New York Times in 2005. The Bush administration was able to dismiss the story, more or less as just allegations. This and similar treatment of other leaked stories was the reason that Snowden released he had to leak hard evidence and lots of it. The PBS Frontline documentary, The United States of Secrets has a good summary of these events.