It might be possible to petition the juvenile authorities to reopen, and dismiss the charges, clearing the conviction record to allow your enlistment. You do not presently qualify under normal procedures to have the convictions set aside as not enough time has past. The fact that there is more than one prior offence may be an issue as well. You should see an attorney with specifics and firm advice based upon it.
Answered on Jan 24th, 2013 at 12:32 PM