Ryan Dennis Archer, 34, admitted importing the class B rated substance Buprenorphine.
The court was told how Archer had arrived in the island by ferry from Portsmouth at 6am in March. He told customs officers he had been to the UK where he admitted using controlled drugs but said he had none with him.
He said he had packed his rucksack himself and was aware of its contents. During a search of the bag, officers found three tablets in a tobacco pouch that turned out to be Buprenorphine with a total weight of 0.85g.
He gave 'no comment' responses to questions in interview and had previous convictions.
Defending, Advocate Sarah Morgan said her client had been going through a difficult time and had been coping with the death of his father.
Deputy Judge Graeme McKerrell said Archer had a long history of drug offending and had been to prison on a number of occasions for offences including supply.
He recognised that this was a relatively small amount and for personal use only but the defendant’s personal circumstances ruled out any community-based penalty. He jailed him for 28 days and ordered forfeiture and destruction of the drug.