Is it legal for an employer to direct deposit a paycheck and then
reverse (withdraw) it without notifying the employee?

If it was a mistake, yes - that's usually in your direct deposit
agreement.  I know I've seen it on all of mine.

Yes, but I would certainly think the employer has the responsibility
to notify an employee that his/her direct deposit was reversed, before
implenting same.  And, isn't it illegal to withhold an employee's pay
past the paydate due, again without notifying the employee?  Can you
imagine all the ramifications to that employee's checking account? 
Mucho dollars in bank charges/returned check fees, overdraft fees,
etc.  Anyone out there that can shed more light?