Our constitution prohibits ex post facto law. This means that someone can't be charged with violating a law that was not in effect at the time of the person's action. ie, if the the speed limit is lowered to 50mph on Tuesday, you can't be ticketed for having driven 55mph on Monday. This should apply to the NSA in the same way that it applies to citizens. We may not like the law, but we can't call them criminals, dictators or all around bad guys for playing by the rules as they were written at the time.
It's also important to note that the NSA currently has the support of the people and the people's representatives. If 80% of the country hated the law that allows blanket collection of business records then it would have been changed long ago. The issue is 50/50 at best among the people and much more lopsided in favor among members of congress. Changing the law will be difficult at this point, as it's supposed to be. The whole point of a democratic bureaucracy is that they are stable and slow to change. We can't routinely re-write laws that are disliked by 40% or even 50% of the people and lawmakers. In general, it's bad for business. It's difficult to plan for the future when a relatively small group of citizens can throw out the rules in a short time period.
If the NSA had some kind of effect on the life of the average citizen this law would be rescinded immediately. If that doesn't end up happening, it's going to take a lot more than personal interpretations of the constitution to get the federal government to give up capability and assets it spent a lot of time and money building. This law may change and the country may be better without it. If anything it will be a long time until the majority of people make up their minds or even form an opinion on this issue. Until then the NSA is going to what all of us do: pursue their goals while acting within the boundaries of the law.