The scope of a proposed law criminalising intellectual property (IP) infringements is being fiercely debated in Strasbourg ahead of a vote by the European Parliament there today.

Some parliamentarians want to restrict the law's scope so that it only applies to infringements on a commercial scale "for the purpose of obtaining commercial advantage." In other words, even a teenager who illegally downloads thousands of songs and inadvertently shares those songs with thousands of other file sharers cannot be liable to criminal sanctions.

Rights holders are enraged by the inclusion of the reference to profit. They argue that this addition undermines the whole law and opens Europe up to charges of hypocrisy – both the European Union (EU) and the US have criticised China for a similar clause in its IP laws that limits legal action only to cases where someone is profiting from an IP infringement.

The reference to commercial advantage was added to the text last month when the draft law was being discussed by the parliament's legal affairs committee.

Since then the Liberal Party in the European Parliament has drafted new amendments that would return the law to its original scope, covering all infringements on a commercial scale.

An alliance comprising the Foundation for a Free Information Infrastructure (FFII), consumer groups and library associations have written to members of Parliament urging them to ignore the Liberal Party amendment. They say it leaves the scope of the law undefined.

"This is a horrible proposal. How will the courts deal with the uncertainty? Ultimately, the European Court of Justice may decide, but what will be its decision? This way the Community would make criminal law without any certainty about the final outcome," said FFII analyst, Ante Wessels.

Another controversial clause in the draft law concerns inciting, aiding or abetting an IP infringement. The wording is ambiguous, argue voices from across the IT industry. And with such severe sanctions at sake, they argue that the law will deter people, especially in the software industry, from being innovative.

Theoretically, any network could find itself liable to criminal sanctions if it carries content that breaches someone's copyright or trademark. An internet service provider could be found criminally liable if a subscriber infringed someone else's intellectual property. Similarly, a software developer could be held criminally liable if he or she inadvertently breached another developer's copyright.

However, in reality the new law won't change much, as many EU countries already have criminal sanctions for IP-related crimes, which are only ever invoked in cases involving major counterfeiting gangs. It will simply harmonise the rules across all 27 countries, argue parliamentarians pushing to get the law passed.

Patents are almost certain to be exempt from the scope of the law, to the relief of IT companies and scientists. The European Commission had originally proposed applying criminal sanctions, including prison time, to patent infringers but the idea was thrown out by the Parliament's legal affairs committee.