Who can I spy on?

Question

With the new Way of Life DLC, if you have Intrigue Focus, you should be able to Spy On other characters.

For characters where the Spy On is available (greyed out or not), the requirements are listed as:

• is not a prisoner
• is an adult
• is within diplomatic range

But for many characters, Spy On is not available:

What are the requirements for that?

Based on my observation it seems that I can spy only on characters in my realm. Is that correct?

Answer 1

Yes, you can only spy characters in your realm.
If the target of your spying leave your realm, like when they manage to escape imprisonment and flee/rebel, you get a popup that tell you that it's pointless to continue to spy on them.