excerpt from above link...
So whats the answer? It appears this gun-free zone type policy can actually be traced back to Department of Defense (DoD) Directive 5210.56, signed into effect in February 1992 by Donald J. Atwood, deputy secretary of defense under President George H.W. Bush.
I notice that the article cites the Army to act on the DoD directive when Clintoon was in the Oval. When I was in, in another service, guys brought their personal weapons on base.