Marshall had been on bail pending an appeal against a three-month sentence imposed by magistrate Tony Murray in September.

District Court judge Martin Blackmore dismissed Marshall's appeal but did reduce the term he would have to spend in jail from three months to two months.

That was based on Marshall having spent another 20 days in drug rehabilitation since appearing before Mr Murray.   

Marshall will now be in prison until early February.

The former detective, who left the police force in March last year when he was medically discharged, has previously been described as having "a street-level dealer" role in the syndicate.

The ring, masterminded by Malcolm John Collins, was involved in transporting the drug ice from Sydney to the Border. 

The local court was told that Marshall had a significant recent history of substance abuse.

A psychiatrist's report said Marshall's self-treatment was entrenched and involved binge drinking in pubs.

"It was then a small step for him to become involved with an old friend and further involved in the world of drug users and drug dealers," the psychiatrist said.

"The unfortunate error of judgement that he made at that time was affected by his sense of abandonment of his former police colleagues.

"It is not insignificant that he chose to engage with 'the enemy'."