I worked at a company with, let's just say, access to a very high profile individual in the UK.
Part of my contract of employment was that I was unable to mention in public or anywhere any conversations that took place involving this individual or reveal details of his whereabouts / meetings etc etc. Upon handing in my notice I was to hand back information obtained through my employment in relation to the company.
Now I'm pretty sure had I kept info and then released it to the media, I could be charged with theft.... but talking about meetings I had or were privvy to conversations etc that took place in the past then they couldn't do a thing about it.