Unlike the Chinese members here, I do read my sources to the fullest. I also read opposing sides as well.
UNITED NATIONS CONVENTION ON THE LAW OF THE SEA
Intelligence gathering are either active or passive. UNCLOS Part II Article 19 point 2(c) is vague as to which method is 'prejudicial' to peace or towards disqualification to the principle of innocent passage. If a foreign warship is claiming innocent passage thru an EEZ and such claim is usually is granted, how do you know if its
PASSIVE intelligence apparatus is not in operation?
If you examine all other sub-points under 2, you will see that those other activities are
ACTIVE measures or actions, such as...
And so on...
Sub-point 2(c) states: any
act aimed at collecting information to the prejudice of the defence or security of the coastal State;
Turning on a radio is technically an action. How else am I going to listen to Lady Gaga if I do nothing? So the context of the word 'act' here is beyond the human ability to perform a physical motion but to include a moral justification as well.
If a foreign vessel merely sits inside an EEZ and do nothing, like how Soviet 'fishing trawlers' often used to do, there is no doubt as to what the vessel is doing or 'acting', which is intelligence gathering. Its non-movement or non-motion is necessary towards its mission. Therefore, its 'act' is obviously -- 'prejudicial to the peace, good order or security of the coastal State.' The vessel may not be actively transmitting anything to its owner state but precisely because it is not moving, its intention cannot be anything else, like mechanical failure that stranded it, but that of intelligence gathering.
But if a warship is moving thru an EEZ as demanded by UNCLOS, and if there is no credible way for the coastal sovereign state to definitively ascertain that this is an intelligence gathering mission, then legally speaking, there is nothing this coastal sovereign state can do.
The context of the word 'act' in 2(c) is hinting at real actions such as communication with an agent inside the coastal sovereign state, or picking up people, or deploying/discarding intelligence gathering devices.
