I can't speak to SIP specifically, but to work at the NIH (or most gov't facilities) you have to consent to a background check, which will ask you about drug use and illegal activities. Obviously you can be as truthful as you choose, but it's technically perjury if you lie (and get caught). Never heard of anyone getting a physical drug test though--although the gov't has the right to perform one if you like, show up to work high or something.