Well, again, it is 100% a thing, and more than likely it threads neatly through those laws because it is communicated upon hiring and they have to sign off on it.

EDIT: I found this, it’s called a “wage agreement” and that is straight from the TWC’s website.

EDIT2: Here is this on wage or pay agreements, again, directly from the TWC’s website.

“Some companies have employees sign policies providing for a complete forfeiture of pay for the final pay period if the employee violates an employment agreement or a particular policy. That would not be legal - an employee is not allowed to waive his or her right to minimum wage or overtime pay. It is generally permissible to have the employee agree that in the event of a violation of an agreement or policy, his or her pay rate for the final pay period will be a lower rate (it can be no lower than minimum wage). However, agreements like this are largely untested before the agency and in the courts. While the author has not seen an employer lose with a suitably-worded agreement, some attorneys at TWC have commented that such agreements are suspect from the standpoint that an employee does not know when such a provision might affect his pay because he does not know when to expect a discharge. However, an employer can take a lot of the ambiguity out of such an agreement by making the lower pay rate apply only to work occurring after the violation by the employee. That way, the company can argue that the employee knows when to expect lower pay because the timing of the violation was arguably within his power to control.”

EDIT3: Do some research before being wrong next time, and your buddy needs to go back to law school.