Cpr Certification Training Is An Employer Allow To Keep Your Training Certification?

Is an employer allow to keep your training certification? - cpr certification training

I was trained in CPR and I paid half of the training.
My boss refuses to give me the certificate. What was not used for the next task.
Their argument is that because he pays half of the studies are able to maintain their certification.

Is it legal to do? I was the one who was trained and I paid half of the training itself.