https://www.techdirt.com/articles/20200820/13395145155/secret-service-latest-to-use-data-brokers-to-dodge-warrant-requirements-cell-site-location-data.shtml

Another federal law enforcement agency has figured out a way to dodge warrant requirements for historical cell site location data. The Supreme Court's Carpenter decision said these records were covered by the Fourth Amendment. But rather than comply with the ruling, agencies like the CBP and ICE are buying location data in bulk from private companies that collect this data, rather than approach service providers with warrants.

These agencies argue they aren't violating the Constitution because the data is "pseudonymized" and doesn't specifically target any single person. But even cops using "reverse" warrants are still using warrants to gather this data. Federal agencies apparently can't be bothered with this nicety, preferring to collect information in bulk and work backwards to whatever it is they're looking for.