Withholding paychecks

I am pretty sure I know the answer but I would like feedback anyway. Our organization recently started using time clocks that require an employee to electroncially approve their timecards. Some supervisors have a hard time getting employees to make the approval in a timely manner or when it is needed. They (the supervisors) what to withhold paychecks until the timecard is approve. I know this is improper under both federal and state law but cannot find anything directly on point. I thinking it violates FLSA because you wouldn't have paid the minimum wage when due and state law that identifies specifically when you can offset wages. I say it is a discipline issue. Any input would be appreciated
Comments
In the past, we have put this type of thing under our "timekeeping procedures" section of the handbook. Good luck!