No legal threats
No legal threats is a rule that is used on Wikipedia and related projects. It prohibits anyone from threatening to sue someone, claiming that someone else has broken the law, or in any way suggesting that what someone has done is illegal. The punishment is banishment from the project, sometimes permanently, which can lead to the person who is actually breaking the law allowed to break the law while the person who notifies them gets banned. The John Seigenthaler Sr. incident proved the ridiculousness of this rule, when someone was banned for daring to say that what was said was libel (even though it actually was). Ultimately, John Seigenthaler Sr. himself contacted Jimbo Wales to threaten to make face to face legal threats, which Jimbo responded to by not only changing the article to remove the libellous content, but to make the article enormous and very flattering towards Seigenthaler. This case, amongst others, proved the sheer ridiculousness of this rule - Wikipedia in actual fact does respond to legal threats when they are given in person. Furthermore, Wikipedia bans people for legal threats even if they were not aware of this rule - and indeed even if they are not actually legal threats, for example someone saying "If you do this, then you will be breaking the law" can and has been grounds for permanent irreversible banishment, even though it is not actually a legal threat at all. Indeed, in some cases someone just giving legal advice can be grounds for a ban.
In normal society, making legal threats helps things to run smoothly. In most places on the internet, legal threats help things to run smoothly. Indeed, even on Wikipedia, ultimately, legal threats help to make things work properly. The oversight command is meant to be used to avoid legal problems. Information regarding potentially libelous edits are constantly being fed to the oversight team from editors and admins, and through OTRS, sometimes from the subjects. These can sometimes be in the form of legal threats.
Wikipedia makes a distinction between bannable legal threats and legal threats that they act towards based on how they are done. Essentially, if you want to legally threaten Wikipedia, you need to call them on the phone (and hence be in USA) or else to contact one of their legal representatives. Making the exact same legal threat on Wikipedia itself can get you banned.