Maryland Code, Insurance § 14-205

(b)(1) A preferred provider insurance policy offered by an insurer under this subtitle shall provide for payment of services rendered by nonpreferred providers as provided in this subsection.

(2) Unless the insurer demonstrates to the satisfaction of the Commissioner that an alternative level of payment is more appropriate, for each covered service under a preferred provider insurance policy, the difference between the coinsurance percentage applicable to nonpreferred providers and the coinsurance percentage applicable to preferred providers may not be greater than 20 percentage points.

(3) If the preferred provider insurance policy contains a provision for the insured to pay the balance bill, the provision may not apply to an on-call physician or a hospital-based physician who has accepted an assignment of benefits in accordance with § 14-205.2 of this subtitle.

(4) The insurer's allowed amount for a health care service covered under the preferred provider insurance policy provided by nonpreferred providers may not be less than the allowed amount paid to a similarly licensed provider who is a preferred provider for the same health care service in the same geographic region.

(c)(1) In this subsection, “unfair discrimination” means an act, method of competition, or practice engaged in by an insurer:

(2) If the rates for each institutional provider under a preferred provider insurance policy offered by an insurer vary based on individual negotiations, geographic differences, or market conditions and are approved by the Health Services Cost Review Commission, the rates do not constitute unfair discrimination under this article.