Can employees agree to waive their FMLA rights?

Q. I have been told the company cannot require an employee to sign a valid release of a potential FMLA claim. We recently have gone through a downsizing. We have a severance policy that provides a nice benefit, but to qualify, the employee must sign a general release promising not to sue the company over any employment-related matter. The release includes any claim under the FMLA. Is that OK? ...