Is the "Malaysian solution" illegal?
The internationally recognised legal status of a refugee is not something granted to a person by any particular country or authority. It is not like a licence, or a visa, or a title. According to the legal definition, a refugee is a person who has a well-founded fear of persecution in their country of nationality or residence because of their race, religion, nationality, membership of a particular social group or political opinion. The key word here is "is".

As a signatory to the Convention and Protocol on the Status of Refugees, Australia has well-established legal obligations towards any person who, according to the above definition, is a refugee. Australia recognises in its domestic legislation that it has these obligations, referring to them in the Migration Act as "protection obligations". They include the obligation not to send the refugee to a place where they would suffer persecution. This is not to be done "in any manner whatsoever" (Article 33). Sending a refugee to a country that is not a signatory, and of which they are not a citizen and where they have no right to remain, obviously constitutes a serious risk that they will either face persecution there or be sent on from there to face persecution elsewhere.

An asylum seeker is someone who claims to be a refugee. As with anything, some claims are genuine, some are not. But the individual asylum seeker does not become a refugee only after their claims have been accepted as genuine by the Australian government. They are refugees as soon as they have that well-founded fear of persecution.

So how does the Australian government know whether it has legal protection obligations in respect of any asylum seeker before it listens to the person's claims and makes an assessment? It doesn't. If it sends the person back without making that assessment, it risks sending back a genuine refugee and therefore being in breach of international law.

Official government figures show that around 90% of asylum seekers arriving by boat turn out to be genuine refugees: http://www.aph.gov.au/library/pubs/bn/sp/AsylumFacts.pdf

That means that, of the 800 asylum seekers sent back to Malaysia, which is not a signatory to the Convention, Australia is likely to breach its obligations under international law in 9 out of 10 cases.