It's more like there's no law that prevents you from doing so. In fact, in America, it is protected by the second amendment.
I agree, there's no law against this but I just want to add a minor correction. "Freedom of speech," in other words "freedom of expression," is protected First Amendment, not the Second, the Second Amendment is about the "right to bear arms."
In a free country, anything that is not prohibited is permitted.
I for one don't wish to live in Iran...
