Doyle had already sought a discharge without conviction at the Palmerston North District Court, which was denied by Judge Bruce Northwood.
He has now taken his case to the Court of Appeal which will decide in several weeks whether to quash his conviction.
Mulgan said that Northwood's decision had failed to take into account Doyle's young age at the time of the offending, and the exceptional circumstances under which it occurred.
"He was devastated that his partner was unfaithful, but she was being unfaithful with his commanding officer, someone he had to take orders from every day and call sir."
"These are exceptional circumstances for anyone to put up with, and he turned to drug use to cope and did some low-level dealing to fund his own habit.
"These are exactly the kinds of circumstances that can drive people to drug use and are not representative of his overall character."
Mulgan argued that the consequences of a conviction outweighed the crime Doyle had committed.
He said that his client was stuck driving a truck after investing his entire life into a military career which he'd since been kicked out of.
His prospects for travelling, studying or getting any job other than basic labouring were slim.
"His entire working life was supposed to be the Army. Understandably he doesn't have a plan B at the moment. He would like to advance himself, but for any role of any substance he will be asked about a conviction," Mulgan said.
"Any attempt to advance himself will be severely handicapped if this conviction stands."
Crown lawyer Anna Davies told the court that to some extent the seriousness of Doyle's offending was offset by the circumstances.
But that the dealing itself was made more serious by the fact he was dealing to other military personnel.
"This is commercial drug dealing. He had $2000 in cash, scales and a tick list. This was not a one-off youthful indiscretion," she said.
The Court has reserved its decision on Doyle's conviction.
