PA-40-Employee rehire action is allowing hired employees to get rehired

Hi experts,

In a very strange situation system is allowing the all ready existing employees to get hired.

It should generally not allow a already active employee to get rehired....rehire should be always for employees who are not active & have left the company.

I tried by coping the MSN-20 feature, but that also is not stopping the system.

please guide me on the same,