Three US think-tanks that campaign against government regulation have asked permission to present arguments in support of Microsoft as part of its appeal against a European Union (EU) antitrust ruling.

One of the three organisations, the International Intellectual Property Institute, has a Microsoft employee on its board of directors. The other organisations are the Progress and Freedom Foundation and the Institute for Policy Innovation.

The three groups have asked to intervene in the hearing for Microsoft's appeal against a ruling by the European Commission, the EU's antitrust regulator. The Commission ruled last year that Microsoft had abused its dominance of the market for PC operating systems to gain control of the markets for media player software and workgroup server software.

The groups' request has been criticised by Microsoft's opponents. The request is an "abuse of the right to request leave" to intervene in the case, according to Carlo Piana, a lawyer based in Milan, who represents the Free Software Foundation Europe in the case against Microsoft. He called for the request to be rejected to avoid creating unnecessary work for the court.

Under the EU's rules for antitrust cases, third parties can ask to put their views across in hearings by the Court of First Instance. The decision to allow them to do so rests with the president of the court, who has to be convinced that the organisation would be affected by the outcome of the appeal and the initial antitrust decision.

The three groups may have argued they are entitled to put their views across because they are claiming that a decision to uphold the Commission's ruling will impair property protection around the world, Piana said.

At present, the parties authorised to intervene in the appeal hearing are, on the Commission's side, RealNetworks, the Software and Information Industry Association (which represents more than 750 companies), the European Committee for Interoperable Standards, and the Free Software Foundation Europe. For Microsoft they are the Association for Competitive Technology and the Computing Technology Industry Association.

Microsoft has links with the International Intellectual Property Institute (IIPI). One of the IIPI's directors is Marshall C Phelps, a corporate vice-president and deputy general counsel for intellectual property at Microsoft, while Susan Mann, federal government affairs manager at the company, is listed on IIPI's website as an advisor to the institute.

The Institute for Policy Innovation (IPI) published an article in December 2004 calling the Commission's antitrust ruling against Microsoft "absurd". The article quoted IPI's George Pieler saying that the Commission's decision to force Microsoft to offer a version of Windows without Media Player was like making refrigerator manufacturers sell freezers, icemakers and refrigeration units separately.

Among the members of the Progress and Freedom Foundation's advisory committee on the Digital Age Communications Act is C Boyden Gray, a lawyer who intervened in favour of Microsoft in the company's antitrust case in the US. Gray is a senior partner at law firm Wilmer Cutler Pickering Hale and Dorr, and has publicly expressed support for Microsoft's position in the case. In July, he was also nominated by US President George Bush as the new US ambassador to the EU.

Commenting on Gray's nomination as ambassador, Georg Greve of the Free Software Foundation Europe said that the selection of what he called Microsoft's antitrust mercenary was "an explicit statement of who truly holds political power". He urged the Commission to stay true to its course in the case and not to let "US company interests rule over those of European consumers and the economy".