The Stop Online Piracy Act (SOPA), which would allow US authorities to seize the domain names of copyright-infringing websites, has taken another blow as a leading proponent has withdrawn its support.

The Business Software Alliance (BSA), which initially supported SOPA, has decided the legislation goes too far.

"Valid and important questions have been raised about the bill. It is intended to get at the worst of the worst offenders. As it now stands, however, it could sweep in more than just truly egregious actors," BSA president and CEO Robert Holleyman wrote.

SOPA would enable the US government to block access to websites internationally. This not only includes the .com domain, but also .net and .org, domain names which are used by millions of organisations outside the country's legal jurisdiction.

"Due process, free speech and privacy are rights that cannot be compromised. And the security of networks and communications is indispensable to a thriving Internet economy. Some observers have raised reasonable questions about whether certain SOPA provisions might have unintended consequences in these areas," Holleyman wrote.

Such a dramatic turnaround seems to be part of a growing realisation that copyright infringement legislation is going too far. At the weekend, European Union Digital Agenda Commissioner Neelie Kroes said,"Citizens increasingly hear the word copyright and hate what is behind it. Many see the current system as a tool to punish and withhold, not a tool to recognise and reward."

"It is simplistic to assume that because some intellectual property protection is good, that such protection should therefore be absolute in all circumstances. Let's ask ourselves, is the current copyright system the right and only tool to achieve our objectives? Not really, I'm afraid. We need to keep on fighting against piracy, but legal enforceability is becoming increasingly difficult," she said.

Meanwhile last Friday the European Parliament added its voice to those calling for SOPA to be abandoned. More than 60 civil and human rights organisations wrote a letter to Congress calling for the rejection of SOPA. The letter argues that the act "is as unacceptable to the international community as it would be if a foreign country were to impose similar measures on the United States."

The Business Software Alliance represents IT companies including Microsoft, SAP, IBM, Dell and HP.