Under minimization rules, no serious argument can be made that Flynn’s identity was not necessary to understand the intelligence significance of his call with the Russian ambassador. The call is foreign intelligence information mainly because it involves Mr. Flynn.

Benjamin Wittes flags that much of the Yahoo story is unclear, including legal arguments and the objective of the search, and further reporting from Motherboard and the Intercept further confuses the possible mechanism of the search, describing it not as a spam filter but like a "rootkit" and opening up a significant vulnerability. 

I have very little sense of what really happened between the government, Yahoo and the FISA court. So I'm going to wait to have an opinion until I actually know something. So should everyone else.

If investigators had wanted to obtain authorization to conduct electronic surveillance or physical search of Omar Mateen, could they have?