Re: leaks..
"...how clearly are politicians informed of the rules..."
Fully.
Security consultant John Schindler hit the nail on the head with an Op-Ed in the Los Angeles Times a couple of weeks ago.
http://www.latimes.com/opinion/op-ed/la-oe-schindler-emailgate-20150825-story.html
To handle classified information in the US, even politicians have to undergo training on handling classified info. (And yes, I have first hand experience handling classified info.)