[jakobsen]

Anybody with some law knowledge can help me get this right?

He says the clause doesn't violate the First Amendment because he is freely agreeing to "forfeit his right to speak freely".

Are constitutional rights not inalienable in the USA then? In my country, in case of conflict laws of "greater range" take precedence over laws of "lower range", and contracts are at the bottom of this hierarchy. That means that a clause as the one being discussed here would be void, since you can't give up your right to speak freely even if you wanted¹ Isn't there a similar concept in the USA??

¹ That also means that if laws mandate 3 weeks of holidays, you can't take only 2 weeks in exchange for a bigger pay even if you wanted (happened to me once).