The system we use to share sensitive information is a joke. It was created many years ago by
Executive Order 13526- Classified National Security Information. It has been reissued by ever president. In this document there are little jewels that show just crazy the system is.
First of all, documents are classified by the issuing agency and if an expiration date or event is not specified in the document regarding expiration then the document automatically declassifies after 10 years. However, the document can declassified by agency at anytime or can be extend and the person who has a copy of the document may not know that.
Copies can be made of classified documents and can be shared with others. The person that the document is issued to has the responsible of seeing that the document is properly used by those who are authorized by their security classification.
If portions of a classified documents are extracted and included in not classified documents, that information still remains classified.
Just because someone has a document marked classified, it doesn't mean the information is actually classified.
In my opinion the whole system is riddled with problems. The only documents that are really controlled are top secret documents and top secret compartmentalize documents.
obamawhitehouse.archives.gov