Melrose utility back Sam Chalmers has admitted to the use of a prohibited substance and faces the prospect of a playing ban, BBC Scotland has learned.
The 19-year-old's case was heard by the International Rugby Board on Wednesday.
However, the level of sanction is yet to be announced.
Chalmers' positive test came from a sample taken after a Scotland Under-20s game against Ireland on 13 May
and his case has already been considered by the World Anti-Doping Agency.
Chalmers is the son of former Scotland and British & Irish Lions fly-half, Craig.
The Scottish Rugby Union will not comment until the IRB's findings are made known.