The First Amendment!
The First Amendment guarantees freedoms concerning religion, expression, assembly, and the right to petition. It forbids Congress from both promoting one religion over others and also restricting an individual’s religious practices. It also guarantees freedom of speech, with exceptions.
Exceptions To The 1st Amendment: exception, and cases of diminished protection. Speech that involves incitement, false statements of fact, obscenity, child pornography, threats, and speech owned by others are all completely exempt from First Amendment protections.