> The use of cell phone data is well understood, well litigated, and for all intents and purposes, settled law.

I don't have strong views on the right policy outcome, but it is not accurate to call this issue well litigated and/or settled law.

Just yesterday, NYTimes ran an article about DIA claiming a "commercial availability" exception to the only Supreme Court case addressing cell phone location data (Carpenter). If that is indeed DIA's rational, they are going to have some problems. For example, it is unlawful for the state to use commercially available thermal optics to surveil the interior of a dwelling without a warrant. I think DIA may be relying on dicta from Kyllo about devices in "common use", but their rational is secret so we won't know until it is... litigated.

[1] https://www.nytimes.com/2021/01/22/us/politics/dia-surveilla...