Legislation designed to force internet service providers to block websites predominantly for the purposes of infringing on copyright, such as The Pirate Bay, could lead to copyright holders getting websites blocked without any test to see whether the sites are predominantly for copyright infringement, lawyers have warned.

The legislation, introduced by Communications Minister Malcolm Turnbull last week, would allow rights holders in Australia to obtain an injunction from the Federal Court to force internet service providers (ISPs) to block websites that provide access to illicit downloads of TV shows, films, music, and other copyright-infringing files.

The sites that the court will be able to rule to be blocked must be based outside of Australia; infringe or facilitate copyright infringement; and have the primary purpose of facilitating or infringing on copyright.

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The court has discretion to rule on how ISPs must block the websites, but the government has indicated that the scheme, regardless of the method of blocking websites, will cost ISPs AU$130,825 annually to implement.

ZDNet has asked the Attorney-General's Department to explain its methodology behind this figure, but had not received a response at the time of writing.

Under the proposal, consumer advocate groups or public interest advocates aren't entitled by default to be a party to the case to argue why the sites should not be blocked. The only parties that can join the case are the rights holders, the ISPs, and the owners of the websites. While third parties can apply, it isn't guaranteed.

But as the legislation only applies to websites based outside of Australia, it is unclear whether any of the sites in question would appear in the court case.

The rights holder would go to court, and, if unchallenged, would have to pay their own costs. However, if an ISP joins the case, it could ultimately have to bear not only its own costs, but also the costs for the rights holders. This means that internet service providers could potentially be averse to contesting the challenges, particularly if the volume of requests for sites to be blocked rises.

According to Shelston IP's Katrina Crooks and Wen Wu, this could lead to the courts simply allowing rights holders to block any website they apply for.

"Assuming usual court procedure will apply to such applications, the respondent, in this case the ISP, is required to appear in the proceedings. If it fails to do so, the copyright owner can apply for default judgment under rule 5.23(2)(c) of the Federal Court Rules 2011. The case law on default judgment suggests that in those circumstances, the copyright owner may not be required to prove its case by evidence," they stated.

"Therefore, notwithstanding the apparently high bar set by the 'primary purpose' requirement, it may be possible for a copyright owner to obtain a blocking injunction without filing any evidence at all."

The Australian Digital Alliance (ADA) agreed that ISPs would likely not contest the cases, leading to little examination of the evidence brought by the rights holders.

"International experience has shown that ISPs have no incentive to contest these applications. As a result, cases are done on the papers without vigorous testing of the underlying claims of infringement," Trish Hepworth, executive officer of the Australian Digital Alliance, said.

The government should allow public interest advocates to contest the cases brought by the rights holders, Hepworth said.

"Copyright is a highly technical area, with exceptions, limitations, geographical licensing, and differing terms muddying the water as to what content is infringing and in which jurisdictions it infringes. That is why it is essential that advocates for the public interest or consumers are able to contest the applications."

Hepworth said that the legislation is also not clear about what types of sites, or how many, can be caught up by the legislation. Although the explanatory memorandum states that the legislation isn't designed to catch virtual private network (VPN) sites, it could be considered to be facilitating online copyright infringement by providing access to content outside of Australia.

"Websites offering legitimate services, such as online stores, cloud storage, cultural collections, and VPN providers, all have the potential to fit within the definitions in the Bill. Further safeguards, such as freedom of speech and freedom of access to science and culture, should be mandated as factors for the judge to consider," she said.

"Public interest advocates should also be able to apply for review or removal of an injunction that is no longer appropriate."

The ADA also warned that there is no oversight of the scheme to ensure that legitimate sites aren't accidentally blocked in the process of blocking sites deemed by the court to be infringing on copyright.

The Australian Securities and Investments Commission (ASIC) caused thousands of legitimate sites to be blocked in 2013 because it didn't understand how IP addresses work.

A parliamentary inquiry into the power that ASIC used to get ISPs to block those sites is due to report back to parliament in July, while a committee investigating the copyright site-blocking legislation is due to report back in mid May.