> I'm not going to argue over principles, as that's not law,

> The Supreme Court declined to extend the third-party doctrine to tracking one's location via cell-phone metadata in Carpenter v. U.S., 585 U.S. 296 (2018), so it's not absolute.

In other words, principles are law -- in the US, whatever the principles of 9 judges at a given time, because they are the final arbiter of what anything written down by Congress means. "Third-party doctrine" is not law as written by Congress, it is something the Supreme Court made up out of thin air according to their principles. And these principles are not binding; a later panel of judges is free to throw out the rulings of older judges if they decide their principles differ, as famously happened to Roe v. Wade among other cases.