Reading between the lines of various NSA statements, it seems like they interpret the relevant sections of the Patriot Act and FISA Amendments Act to only apply

Reading between the lines of various NSA statements, it seems like they interpret the relevant sections of the Patriot Act and FISA Amendments Act to only apply to "collected" data, and "collected" data they consider only that which a person looks at and stores. Apparently, they think that the restrictions imposed on them don't apply to automated machine reading of data, or any data that might possibly (51% or more) have a foreign source or destination. Since they define the criteria for what is "interesting", it gives them the ability to inspect essentially all of the data they collect, and there is at present no real check on the loosening of what constitutes "interesting" over time.