unusual and extraordinary threat to the national security and foreign policy of the United States

[selfmade]

Like, find 10 differences:

http://www.whitehouse.gov/the-press-office/message-congress-continuing-national-emergency-with-respect-syria
http://www.whitehouse.gov/the-press-office/2012/05/09/message-continuation-national-emergency-respect-actions-government-syria
http://www.whitehouse.gov/the-press-office/2014/02/20/notice-continuation-national-emergency-respect-libya-idls-and-notice
http://www.whitehouse.gov/the-press-office/2014/03/06/executive-order-blocking-property-certain-persons-contributing-situation

What's up with officialese "unusual and extraordinary threat to the national security and foreign policy of the United States"?
Where does it come from?
What's the actual meaning?
Seems to be catch-all clause.