This page should eventually contain a fairly detailed discussion of possible legal issues that editors need to be aware of. For now, it is just an outline sketch, please add to it as needed.
First Amendment 
Universal Declaration of Human Rights 
The Universal Declaration of Human Rights, particularly articles 18 and 19 are often cited by people outside the United States as being grounds for the existence of freedom of speech, expression or of the press in those countries. The Universal Declaration is, however, not a treaty and is in no way legally binding. Citizens of countries with no constitutional freedom of speech or the press should refer instead to the International Covenant on Civil and Political Rights, which is a treaty and binds signatory states by international law.
International Covenant on Civil and Political Rights 
The International Covenant on Civil and Political Rights is a ratified treaty granting certain rights, defined within that treaty to the citizens of those signatory countries which have ratified it. Some countries have specific declarations and reservations regarding certain rights as defined in the main text of the treaty. Article 19 covers freedom of speech, expression and the press.
Libel is the publication of deliberate and malicious falsehoods which are shown to be damaging to someone's reputation. Libel suits may be made in different juristictions, which may have different standards for deciding if a case before it can be ruled as libel.