‘Julian Assange is free’: Wikileaks founder freed in deal with US

That's an expansive definition that also describes what a journalist does, which is what upset defenders of civil liberties about the prosecution of Assange. The usual connotation of the word espionage, however, is that it is done by an organization, against adversaries, for its own benefit. Assange was explicitly seeking information from whistleblowers to release to the world. Like a journalist.

But to my point, the CIA explicitly engages in espionage as its mission. So would President Xi be justified in sending his police to the environs of Langley to drag CIA employees out of their beds and before a court to stand trial in Beijing? I say no, because they're American citizens in the United States. Chinese law should not apply here in America.

Traditionally, courts need to have jurisdiction to hear a dispute, and it comes in multiple types: There's subject-matter jurisdiction; a municipal traffic court has subject matter jurisdiction over traffic infractions. It can't hear a murder case. Then, there's personal jurisdiction, meaning it has power to compel an appearance by a defendant, and impose penalties or assess damages. Personal jurisdiction usually comes from citizenship, or physical presence. State and federal courts have wide-ranging personal jurisdiction, but even then they have to "reach out and touch someone" with service of a summons to effect it. (Trial in-absentia is not allowed in the U.S. unless the defendant waives the right to appear.) Tangentially, the admiralty law system developed because of a lack of a country's courts' personal jurisdiction over foreign nationals, and suing property (the basis of civil forfeiture) came about due to sailors simply returning to their home countries, out of legal reach.

Thus, the idea of prosecuting a foreign national outside of the U.S., for actions undertaken outside of the U.S., in places where U.S. law shouldn't apply—essentially extending a U.S. court's personal jurisdiction to the whole planet—is deeply troubling. Even if it's just one category of crime, like espionage. If there's one exception, then there's no practical protection, since a country can define espionage in any way it wants to trigger the exception. Or not. It could just accuse somebody of espionage, evidence be damned. After all, that person would be hauled off to a foreign land before being able to mount a defense in court.

That is a tool of tyrants.