Training Certificate & Sponsorship

I have a staff just complete a company sponsorship course, as per our company policies, we will keep this staff’s certificate for one year to protect the company benefit, however we not mention this point to the staff when he signed his contract.  Now, he try to request management to return his certificate right now. May I check with you as an employer, whether we have the rights to keep the staff’s training certificate?
For your information, there is a clause in his contract as following: It is understood that the sponsorship will be withdrawn by company under the following circumstances: -- You resign within one year from the date of completion of the course.
The answer is that the staff shall be given the training certificate as the mentioned clause is “sponsorship will be withdrawn” as your company reserves the right to recover the sponsorship cost but not retaining the certificate.