A tougher approach to serious gun crime is being proposed by the South Australian Government, allowing some offenders to be sent straight to jail.

Under proposed laws, some people charged with a serious firearms offence will not be granted bail, apart from in exceptional circumstances.

SA Attorney-General John Rau said a new category of offences would send some offenders to prison immediately.

He said it would impose prison sentences for serious firearms offenders and widen the number of other offenders who were banned from possession of guns or ammunition.

"Firearms offences are among the most serious and dangerous breaches of the law. Guns are the weapon of choice for organised crime gangs," he said.

"We need heftier sentences and new ways to control the behaviour of serious firearms offenders and these reforms will deliver just that. At the same time these changes will have no impact on law-abiding owners of registered guns.

"I'm not pretending that every single firearms offence will disappear overnight, that clearly is not credible, but I think the decision of these individuals to make the journey from home to wherever they're going with a firearm will be something that they will make with much more reflection after this comes in."

Criminologist Professor Mark Findlay of Sydney University said the proposed laws undercut the fundamental premises of justice.

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He said making suspected criminals prove why they should get bail was too radical a break from legal tradition.

Professor Findlay argues rather than trying to deter criminals in the heat of the moment, governments should be restricting the supply of guns.

Proposed legal change A new category will include anyone who commits an offence against the Firearms Act or the Criminal Law Consolidation Act involving firearm use:

• When that person is on parole, home detention, bail or a suspended sentence, or released on licence, if a condition of that person's liberty is that he or she be prohibited from possessing firearms or ammunition.

• When that person is subject to a control order under the Serious and Organised Crime (Control) Act.

• That involves in any way a firearm that is prohibited.

• That involves in any way a fully-automatic firearm.

• That involves an unlicensed person using an unregistered hand gun.

• That is in breach of a firearms prohibition order.

• If the offence was committed in connection with a serious drug offence. (Source: Attorney-General's office)