For US law on this subject, check out the Third Party Doctrine. There's a good article by Orin Kerr on it, which is a defense of the doctrine but also goes over

For US law on this subject, check out the Third Party Doctrine. There's a good article by Orin Kerr on it, which is a defense of the doctrine but also goes over its fundamentals(https://repository.law.umich.edu/cgi/viewcontent.cgi?article=1348&context=mlr https://repository.law.umich.edu/cgi/viewcontent.cgi?article...)