The treaty is an addition to the European Convention on Cybercrime which, in November 2001, became the first international treaty on crimes committed via the internet – dealing with problems of computer-related fraud, child pornography and hacking.
That Convention, drawn up by the Council of Europe, has been signed by 32 countries, including the UK and the US.
However, the new Protocol on "the criminalisation of acts of a racist and xenophobic nature committed through computer systems" is likely to garner less universal support, explains Jon Fell, a partner with international law firm Masons and co-founder of on-line legal service Out-law.com.
"The US is not going to go for this. The ban on hate speech was originally part of the Convention on Cybercrime, but had to be dropped when it became apparent that the US would not support the Convention if it encroached upon its constitutional right of free speech."
The differing attitude between the US and Europe to freedom of speech was the subject of a high profile legal battle between French anti-racism groups and Yahoo! which concerns the sale of Nazi memorabilia by an internet auction hosted by the US portal.
Fell explains:
"The French groups protested that the sale was contrary to French anti-racism laws; Yahoo! argued that the sale was hosted in the US and compliant with US law. A French judge found in favour of the French groups; a US judge then told Yahoo! that, basically, it could ignore the French decision because it would otherwise fetter the US right of free speech. The appeal is ongoing in California."
But individuals cannot escape the new regime by putting their comments on US-based web sites. The Protocol looks at the actions of an individual – not where the equipment is based. So a British citizen cannot expect to evade prosecution by hosting his web site on a server in the US.
Under today's agreement, if implemented into UK law, the sending of a racist or xenophobic e-mail will become a criminal offence, as will denial, approval or justification of the Holocaust or any other genocide. Under the UK's Public Order Act of 1986, it is already an offence to incite racial hatred.
However, Fell notes that there have been no successful prosecutions under this Act in relation to material on the internet. The new Protocol takes these provisions much further and clears up that law's ambiguity about what is covered.
The Protocol only covers material that is made available to the public. Racist comments posted to a web site – whether your own or on the message board of another's – are forbidden under the Protocol; private e-mail is not.
Most expect the UK to sign the Protocol, but that is only a small step towards it coming into force. The Convention on Cybercrime itself has still to come into force because at least five countries must ratify it.
Although many have signed the Convention, to date, only Albania and Croatia have ratified it. The Protocol must wait its turn, because it will not come into force before the Convention.