This has been grinding my gears all day. It sounds to me like the law is poorly written, so he just agrees that it has to be upheld or the FBI can't do it's job. Section 702 allows for collection of the CONTENT of communications, NOT just metadata.
“It would be a strained reading” of the statute, he wrote, “to permit F.B.I. personnel to retain and disseminate Section 702 information constituting evidence of a crime implicating a United States person for law enforcement purposes, but to prohibit them from querying Section 702 data in a matter designed to identify such evidence.”
If the FBI can use the evidence it legally collects, it should be able to use it i guess. Of course they have to give written reasons to request data in the first place, but the legalese makes it sound like they can still use data that they find by 'accident'. Apparently these 'accidents' happen all the time, possibly hundreds of times per year. Of course the actual numbers of these accidental incidents are classified, but still reported for "transparency."
The NSA operates so close to the edge of legality that they can't avoid even unintentionally breaking the law on a regular basis. You can see the reports yourself.
Why should this decision have been kept secret for the last 5 months doesn't really make sense to me either. I guess the intelligence community expects us to be happy they told us at all.