If you read the article it states that General Alexander addressed the legal basis.
And just how is anyone supposed to evaluate the soundness of the legal opinions rendered by the FISA courts since their legal opinions are sealed?
The FISA courts have produced significant rulings and new interpretations to the 4th Amendment that no one but a select few are privy to. Are we to have a furtive judicial system where only a select few actually even know what our laws say and mean?
In a letter to one of his officers written in 1777, Washington wrote that secrecy was key to the success of intelligence activities:
Secrecy, of course -- this is always required in war and intelligence activities. But seeing as how he fought against general warrants issued by the crown, I have no doubt that he would be horrified at the scope and breadth of the NSA's broad collection policies.
For some mind numbingly stupid reason people keep wanting to reveal US intelligence operations to all, citizen or noncitizen alike. That isn't likely to end well.
For a robust demonstration regarding the need for (public) whistle blowers just look at nefarious characters like J. Edgar Hoover and Nixon who used the government's intelligence apparatus as a sword against their personal and political enemies. What place is there in this logic for whistle blowers who should expose those who are acting outside the legal confines of our great nation (e.g. Hoover, Nixon, etc.)?