It is not a crime to enter Australia without authorisation for the purpose of seeking asylum. Asylum seekers do not break any Australian laws simply by arriving on boats or without authorisation.
Article 31 of the Refugee Convention clearly states that refugees should not be penalised for arriving without valid travel documents. What may be considered an illegal action under normal circumstances (e.g. entering a country without a visa) should not, according to the Convention, be considered illegal if a person is seeking asylum.
Australian and international law make these allowances because it is not always safe or even possible for asylum seekers to obtain travel documents or travel through authorised channels. Refugees are, by definition, people fleeing persecution and in most cases are being persecuted by their own governments. It is often too dangerous for refugees to apply for a passport or exit visa or approach an Australian Embassy for a visa, as this could put their lives, and the lives of their families, at risk. Refugees may also be forced to flee with little notice due to rapidly deteriorating situations and do not have time to apply for travel documents or arrange travel through authorised channels.
In other cases, refugees may be unable to obtain travel documents because they do not have identity documentation or because they cannot meet the necessary visa requirements. Australia has very restrictive policies which work to prevent citizens of countries where persecution is widespread from getting access to temporary visas of any kind. These policies leave many people seeking to flee to Australia with no way of entering in an authorised manner.
Permitting asylum seekers to entry a country without travel documents is similar to allowing ambulance drivers to exceed the speed limit in an emergency – the action may ordinarily be illegal but, in order to protect lives at risk, an exception is made.