Sam Chalmers, the 19-year-old Melrose back whose father played 60 times for Scotland, is understood to have failed a drugs test carried out ahead of the under-20 side's friendly match against Ireland in May.
The game was part of Scotland's preparations for the Junior World Cup, held in France the following month.
It is unclear whether the substance involved is a recreational or a performance-enhancing drug.
The International Rugby Board will announce its findings in the case this week.
Sources have indicated Chalmers is not contesting the findings.
Chalmers, who has spent most of the summer in Australia, has not been involved in Melrose's pre-season preparations and did not take part in the club's opening game of the season.
The Herald was unable to contact Craig Chalmers, who is currently coaching in England, last night.