There is no regulation of either wartime or peacetime espionage with regard to what can be spied upon.

Do spies fall under the Geneva Convention?

Article 5 of the 1949 Geneva Convention IV provides: “Where in occupied territory an individual protected person is detained as a spy … such … [person] shall nevertheless be treated with humanity, and in case of trial, shall not be deprived of the rights of fair and regular trial prescribed by the present Convention.”

Can someone be an espionage?

A person who commits espionage is called an espionage agent or spy. Any individual or spy ring (a cooperating group of spies), in the service of a government, company, criminal organization, or independent operation, can commit espionage. ... Spying involving corporations is known as industrial espionage.