This is a slightly messy post, because I do not have the time to make a cleaner one.
The central problem is this: Libel and defamation laws (in Australian law, defamation is anything spoken and libel is anything printed, recorded or transmitted, but we can safely ignore that distinction) exist for the very important purpose of protecting the very valuable social and professional reputations of members of society. But, they are all too easily twisted into a tool for the suppression of dissent or criticism of those in power, or those who have the power of money or the ear of politicians or the courts.
These problems are well recognised - click the "FOE" (Freedom of Information) tag on the left to see a couple of other posts discussing this, or google the chilling effect of libel.
In terms of world libel laws, the UK and Australia are well recognised as being plaintiff-friendly (i.e., it's very easy to sue someone successfully) and the USA, buttressed by their First Amendment right to freedom of speech, is extremely defendant-friendly - if you try and sue someone, you'd better by really positive that you have a case.
In the UK, in recent times, Guardian columnist, blogger and qualified MD Ben Goldacre was sued by vitamin pill salesman Matthias Rath over statements made by Ben that he, Rath, was trying to sell a useless product to people who needed proper medical care. The Guardian, to their credit, backed Ben and the case eventually went in the right direction.
More recently, columnist, author and blogger Simon Singh has been sued by the British Chiropractic Association for saying that it, the BCA, was promoting therapies that had not a shred of evidence to back them up. There are many, many commentaries online about this. Google, or go to Bad Astronomer for a starting point.
The key problem is this: Singh, and Goldacre before him, are making statements of scientific truth - given therapies do, or do not, work. These claims may be correct, incorrect or partially correct under given circumstances, but they are statements which can be assessed scientifically. The statement that a given person or organisation is peddling bogus therapies is therefore dependent upon a scientific test.
The courts are most emphatically not the place where science should be determined. Not for evolution, not for homeopathy or mega-vitamin therapy, not for chiropractic "medicine". The BCA are using a legal trick in their suit - complaining not that Singh was accusing them of promoting falsehoods, but that Singh was accusing them of knowingly misleading the public, which is of course a claim which directly impacts upon their reputation.
Ignoring, for one second, the Evidence Based Medicine position that the BCA may not deserve to have a good public reputation, we can come to two either-or conclusions: Either chiropractic treatments are worthless, in which case the BCA is deliberately misleading, or speaking in ignorance, or: Chiropractic treatments are worthwhile, in which case Singh made an incorrect allegation either way.
Now: Wouldn't it be so much better for a body which claims medical authority to defend themselves on the basis of medical worth and scientific validity first, so that they can dump the full weight of bullshit upon Singh, rather than just "He's picking on me!"? Well, of course not - they know they'd lose.
Either way, the courts should not now, nor should ever, have any authority over science. Courts attempt to discover truth (of a sorts) via a given set of techniques. Science attempts to discover the truth via its own set of techniques. Occasionally, they look similar. Never, however, is a court the correct avenue for deciding what a scientific truth is. And the efficacy of chiropractic treatments is a matter of scientific truth.
Therefore, the button I have just added on the top left - Keep Libel Laws out of Science, by the British group SenseAboutScience.org.uk. Unfortunately, the layout may not be friendly to the width of the button.
I wish Singh all the best for his appeal against the atrocious preliminary ruling.