Bassett confirmed that Australians will have no recourse to determine what has been blocked, once it is on the blacklist.

"If you have a situation where what is being banned is never made public, then how do we know that there hasn't been an extension beyond material which infringes censorship publication, for example a political party or some people that might be defined as a terrorist organization? The content becomes based upon whatever might be the whims of the people controlling those filters and the services that report to the filters," he said.

Bassett said the EFA's unsuccessful bid to access the ABA's list of banned online content under FOI laws means that particular legal avenue to establish what falls under mandatory filtering is a no through road. Australians, he reminded, have no explicit freedom of speech within the constitution.

"There are cases under the constitution where for example there is freedom of speech in relation to political expression, and that's been held in a number of cases. For example, in the future if you did find or were able to get evidence showing that some political group has been added to these filters, particularly at the ISP level that never gets seen by people, there might be some room for challenge there. But if those filters don't get published, how will you ever know?"

Bassett said the term "illegal" in an online context is ambiguous, where child pornography, defamatory material or content that violates copyright infringement could all be considered "illegal" content.