SA gun traffickers face mandatory jail

The South Australian government will classify firearms trafficking as a serious offence, opening up offenders to mandatory jail time.

Acting Premier John Rau says the change, to be introduced to state parliament on Wednesday, means offenders can only have a jail term suspended in exceptional circumstances.

"Our message for offenders is if you put a gun in the hands of an unlicensed person, then you must be prepared to wear the consequences."

Mark MacPherson, whose son was killed in 2012 by someone with a gun sold illegally and who has campaigned for changes, said South Australia now had the best gun laws in the country and possibly the world.

He said the changes offered a strong message to those who supplied illegal guns.

"The message is don't bring your rotten trade to South Australia," he said.

Mr Rau said those who traded in illegal guns needed to be held to account.

"These people are actually merchants of death," he said.

Opposition Leader Steven Marshall said he would support any tougher restrictions on illegal guns in SA.