(b) When a chief law enforcement officer's certification is required by federal law or regulation for the transfer or making of a firearm, the chief law enforcement officer shall, within 15 days of receipt of a request for certification, provide the certification if the applicant is not prohibited by State or federal law from receiving or possessing the firearm and is not the subject of a proceeding that could result in the applicant being prohibited by State or federal law from receiving or possessing the firearm. If the chief law enforcement officer is unable to make a certification as required by this section, the chief law enforcement officer shall provide the applicant with a written notification of the denial and the reason for the denial. Nothing in this section shall require a chief law enforcement officer to make a certification the chief law enforcement officer knows to be untrue, but the chief law enforcement officer may not refuse to provide certification based on a generalized objection to private persons or entities making, possessing, or receiving firearms or any certain type of firearm the possession of which is not prohibited by law.