Under what circumstances may an employer request subsequent recertifications of a medical condition?

medical condition? (See 29 CFR § 825.308) (a) The employer may require that the eligible employee obtain subsequent recertifications on a reasonable basis, provided the standards for determining what constitutes a reasonable basis for recertification may be governed by a collective bargaining agreement between such employer and a labor organization which is the collective bargaining representative of the unit of which the worker is a part if such a collective bargaining agreement is in effect. Unless otherwise required by the employee's health care provider, the employer may not require recertification more than once during a thirty-day period and, in any case, may not unreasonably require recertification. (b) The employer shall pay for any recertification that is not covered by the employee's health insurance. No second or third opinion on recertification may be required.