Yes, that's the law, but as I mention in response to another comment, you only defer to the letter of the law if you have/want an adversarial relationship with an employer.

Most major employers include the waiver as part of their onboarding process, and if you refuse to sign, although legally they cannot do anything, in practice you're going to start off on the wrong foot with that employer.

Likewise, if you turn around to your manager and refuse to work more than 48 hours (having not signed a waiver), although legally they cannot punish you for that, it's hardly going to help your career.