The focus on the law follows two cases exposed through the Herald on former servicemen wearing medals which misrepresented their careers.
Rob Clark of Kaukapakapa presented himself at an RSA service as a former NZSAS trooper, replete with the distinctive winged dagger beret and a citation for bravery from US President George W Bush.
The following week, former local RSA president Bill Kerr of Mangawhai was convicted under the medals' law and fined $250 for presenting himself as a Vietnam veteran having never served there.
Both cases were literally close to home for Mitchell, the current electorate MP for Rodney, north of Auckland.
Mitchell said he had sought advice from the NZ Defence Force and been told it was rare for people to present themselves wearing medals they had not earned.
He said NZDF was aware of five cases since 2008, and those showed there was not always malicious intent behind the misrepresentation.
"However, not all these incidents resulted in prosecution. In two cases it emerged that the individuals were in poor mental health, and the matter was dropped after Police spoke to the people concerned."
He said he had talked to Barclay about his bill and supported him pushing ahead to make it law.
"The legislation as it stands is nearly 100 years old, and we should make provision to take a much stronger stand against those who set out to disrespect the service of others and the sacrifices they have made - in some cases, giving their lives for their country."
Mitchell did not respond to questions about whether the bill would be adopted by the Government or stay as it is - waiting to be drawn from the ballot of private members bills.
Barclay, who is a National MP, said it was up to the minister as to whether his proposed legislation was adopted as a government bill.
However, he said he would want to see the proposal to go through a full select committee process to allow comment on the threshold. He had based the maximum $5000 punishment and six months in prison on laws overseas.
Lawyer Graeme Edgeler reviewed the law for the Herald and said it was functional. He questioned the need for a specific law around unauthorised wearing of medals - unless the person was committing fraud.
"People shouldn't falsely claim to have served in the military, and people shouldn't falsely claim to have been decorated for valour, but the appropriate response to anyone who does it is public derision.
"If you do this, people will find out about it, and they will think less of you, and you may suffer as a result."
The law doesn't include those who wear medals earned by family members. The practice of family wearing medals of veterans who have died has grown in recent years. In these cases, the medals are to be worn on the right chest-side, showing that the wearer was not the person who won them.