I asked the same question a number of years ago and pretty much got the standard response, as follows:
"Each candidate's juvenile mischievous background and experimentation of drug use is evaluated in totality, and on an individual basis. Our selection process is very thorough and includes several in-depth interviews, and a background security investigation. Keep in mind that one of the criteria we evaluate our candidates on is life experience. When a candidate discloses illegal activity, we will discuss the incident or activity with you. The Recruiting Unit will assess the activity and a disposition will be determined. Complete disclosure throughout our process is crucial to a successful application. All applicants must be a minimum of three years clear of detected or undetected criminal activity. This requirement includes past drug use."
;D