Investigations into allegations of illegal drug possession is a matter for the police, who must prioritise resources towards tackling crime, including drugs crime with a focus on those offences which cause the most harm.
Any prohibited substance found in a rugby union footballer's bodily specimen that is collected as part of the National Anti-Doping Organisation's testing programme will be fully investigated in line with the anti-doping rules of the sport. Any illegal drug consumption that is suspected and indeed detected as part of a sport's illicit drug programme (akin to employee drug testing) remains within the remit of the National Governing Body to action.