29 C.F.R. § 541.4
The Fair Labor Standards Act provides minimum standards that may be exceeded, but cannot be waived or reduced. Employers must comply, for example, with any Federal, State or municipal laws, regulations or ordinances establishing a higher minimum wage or lower maximum workweek than those established under the Act. Similarly, employers, on their own initiative or under a collective bargaining agreement with a labor union, are not precluded by the Act from providing a wage higher than the statutory minimum, a shorter workweek than the statutory maximum, or a higher overtime premium (double time, for example) than provided by the Act. While collective bargaining agreements cannot waive or reduce the Act's protections, nothing in the Act or the regulations in this part relieves employers from their contractual obligations under collective bargaining agreements.
29 C.F.R. §541.4