I was curious about this so I did a little Googling:
On January 1, 2008, Public Law 110-181 (The Bond Amendment) repealed Title 10 U.S.C. 986 (Smith Amendment).
The Bond Amendment repealed 10 U.S.C. section 996 formerly known as the Smith Amendment, and places restrictions that are similar to the Smith Amendment, but which apply to all Federal Government Agencies. The Bond Amendment bars persons from holding a security clearance for access to SAPs, Restricted Data and SCI if they have been:
* convicted of a crime and served more than one year of incarceration.
* discharged from the Armed Forces under dishonorable conditions.
* determined to be mentally incompetent by a court or administrative agency.
Fortunately I have not personally had to deal with this. But are these lifetime exclusions?
By the way my google searching turned up some older articles related to this topic on clearancejobs.com as well.