It's a little relevant, because the point that non-Americans cannot complain about violations of the First Amendment, because they don't have First Amendment rights, is relevant to both situations.
Aside from that it's not very relevant. Courts have much broader powers to subpoena information than the police. They can get pretty much anyone to turn over any information, or testify about anything, with certain narrow protections (e.g. 5th amendment, certain common law privileges like spousal privilege or attorney-client privilege, etc), as long as the information is relevant to an ongoing litigation.[1]
[1] That is, incidentally, the key constraint on the power. Courts' subpoena power can reach deeply but within a narrow scope. That's why the "fishing expedition" question raised in the article is so relevant. It's not wrong for a judge to rule that a defendant can access peoples' e-mails. It is wrong if that allows the defendant to go on a fishing expedition with regards to people who have no connection to the litigation.
Aside from that it's not very relevant. Courts have much broader powers to subpoena information than the police. They can get pretty much anyone to turn over any information, or testify about anything, with certain narrow protections (e.g. 5th amendment, certain common law privileges like spousal privilege or attorney-client privilege, etc), as long as the information is relevant to an ongoing litigation.[1]
See: http://www.law.cornell.edu/rules/frcp/rule_45.
[1] That is, incidentally, the key constraint on the power. Courts' subpoena power can reach deeply but within a narrow scope. That's why the "fishing expedition" question raised in the article is so relevant. It's not wrong for a judge to rule that a defendant can access peoples' e-mails. It is wrong if that allows the defendant to go on a fishing expedition with regards to people who have no connection to the litigation.