OPINION: People smugglers fall into a special category in Australia, with a reputation almost as low as paedophiles and terrorists. The law reflects this by imposing harsh sentences, and even mandatory minimum periods in jail. This uncompromising response has created a problem. Penalties are imposed indiscriminately in a way that catches children and other unwitting people in the net.

The community reaction to people smugglers is understandable. No one should profit from actions such as the trafficking of women for the Australian sex trade.

Those who make a business of transporting asylum seekers to Australia are especially reviled. Hundreds of people have died en route, with one incident causing Kevin Rudd, as prime minister, to declare that ''people smugglers are engaged in the world's most evil trade''. Lest people did not get the point, he went on to say they ''are the vilest form of human life'' and should ''rot in hell''.

With comments like this from our political leaders, it is not surprising that people smugglers are treated severely by Australian law. Under the Migration Act, a person who assists an asylum seeker to come to Australia can be jailed for up to 10 years. The imprisonment doubles to 20 years where five or more asylum seekers are involved.

Assisting five or more asylum seekers also attracts a mandatory minimum sentence in jail. This is extremely unusual under Australian law, where the courts are usually given the power to tailor the sentence to fit the crime.

Instead, a court must in this case sentence a person to at least five years' imprisonment. The judge must impose this minimum even where it is demonstrably unjust or mitigating factors suggest the need for a lesser penalty.

To attract a mandatory minimum sentence it need only be shown ''on the balance of probabilities'' that a person was aged 18 or over when the offence was committed. This test is much easier to satisfy than that of ''beyond reasonable doubt''. It enables people to be subjected to very long mandatory terms of imprisonment even where there is considerable doubt as to whether they are, in fact, adults.

This doubt may arise due to the difficulty of determining a person's age. Many have argued that the wrist X-ray method set down by the law is unreliable. The federal government has recently said that other measures can now be used, such as dental X-rays and interviews, but great uncertainty still remains.

A substantial body of evidence has come to light showing that 20 or more children have been mistakenly treated as adults and, as a result, have been detained for lengthy periods in immigration detention and even in adult prisons. The problem has attracted media attention and is now the subject of an Australian Human Rights Commission inquiry.

The problems created by our people smuggling laws do not only affect children. Since the offences were put into the Migration Act in 1999, more than 900 people have been prosecuted for bringing five or more asylum seekers to Australia. A spike in the number of prosecutions is expected in the next few years due to the number of boats now arriving in the country.

The large number of people tried is at odds with the fact that the law has very rarely, perhaps only six times, been applied to the organisers of the people smuggling trade. They do not come to Australia on the boats, and are usually clever enough to escape capture in Indonesia.

Instead, the people convicted in Australia are overwhelmingly those who have been enticed to crew the boats. Many are Indonesian fishermen living in poverty with little education. They can themselves be victims of the trade. Like asylum seekers, they bear the risk of death at sea. In some cases they may have been tricked into taking the job, or been lured by the promise of great riches, which may amount to as little as $150.

Australians may not like people smugglers but this does not excuse unjust laws. The organisers of the trade should be subject to severe sanctions. However, mandatory minimum sentences are not appropriate even for them.

It is also wrong to apply the same penalties to people caught up in the trade due to their own ignorance or economic circumstances. This is especially problematic when it extends to children. 

George Williams is UNSW's Anthony Mason Professor of law .

This opinion piece first appeared in the Sydney Morning Herald.