The Spy who Came in from the Cold War: Intelligence and International Law

Discusses obtaining information covertly without knowledge or permission of the controlling state. Is it legal with reservations or is it illegal but still routinely practiced? If states are responsible for covert intelligence gathering, the states could be subject to ramifications if international laws are violated. Intelligence and counter intelligence gathering are very important, and it is very important to have timely access to accurate intelligence. How can intelligence be used? How do legal regimes define norms of intelligence gathering?