In March the US Supreme Court will decide whether controversial new Internet censorship laws are a breach of civil rights. The case is likely to set a global precedent in the ongoing debate about freedom of speech in cyberspace.

The court will consider a government appeal against a federal court decision which found that the newly introduced Communications Decency Act (CDA) violates freedom of speech rights.

But in practice, the court's decision will have far wider ramifications.

Although the CDA's purpose was to protect minors from indecent material on the Net, its introduction has sparked a storm of protest across the US.

Jerry Berman, director of the Center for Democracy & Technology (CDT), claims that: 'This is the most important First Amendment case to come before court in recent memory.'

The CDA was introduced last February as part of a wider Telecoms Reform Act, sponsored by Democratic senator James Exon. Exon is one of the most hardline pro-censorship figures in US politics. His rhetoric is effective: 'The worst, most vile, most perverse pornography is only a few click, click, clicks away from any child on the Internet,' he said recently.

Exon faces strong opposition to his campaign for tighter regulation of Internet content, notably from the controversial Republican Speaker of the House of Representatives, Newt Gingrich.

The Supreme Court will end the political arguments once and for all.

According to Berman's free speech pressure group, the Act falls down constitutionally on a number of points, not least of which is vagueness of terminology. It criminalises not only obscene communications, but also those which are 'lewd, lascivious, filthy or indecent', which are still protected by freedom of speech.

The CDT claims that this leaves legitimate Web sites, such as safe sex bulletin boards, open to attack by censorious groups or individuals.

The Act was quickly seized upon by many groups. Last April, the American Family Association, a conservative Christian group, cited the Act when it demanded that the Justice Department mount a criminal investigation into CompuServe's bulletin board services.

The CDT also objects to a frequently drawn analogy between the Internet and other media, particularly television. The interactive format of the Net, it argues, means parents should be able to control their children's access, so government protection is unnecessary.

Furthermore, the group claims that by criminalising the content of non-obscene private email, the CDA provides a mandate for invasion of privacy.

Service and content providers could be scared into pre-screening all material they carry.

These arguments have so far received two public airings in the US lower courts - in Philadelphia and New York. The Philadelphia court found that the Act was unconstitutional and restricted freedom of speech, ruling that the Internet deserved legal protection as broad as that given print media.

It also decided that it was up to parents to use technical solutions to block children's access to the Net.

The second challenge to the Act came in June from Joseph Shea, publisher of online newspaper The American Reporter. Shea was concerned that the Act put limitations on him, as an online publisher, which are not applied to print media. This was, he said, an attack on the freedom of the press.

A Manhattan court upheld his claim and, crucially for the CDT, also supported the Philadelphia court in its decision that the Net and television were not comparable media.

'Indecent material on the Internet ordinarily does not assault the user without warning,' wrote the New York judges. 'A child cannot gain access to Internet content with the touch of a remote control.'

And so the debate rolls on to its final stage - the Supreme Court. The ruling that emerges here will be based on arguments over points of law, not on the nature of the Net.

Whatever the finding of the court, it is certain to have an impact outside the US. If the CDA is ruled to be unconstitutional, then the court will afford protection to most current Internet content, as long as it is produced in the US.

If it is ruled to be constitutional, then the enforcement of the Act will change forever the way US service and content providers do business.

And with the amount of influence they have over the global market, that would mean changes for everyone.