(a) The board of trustees or a health benefit plan under this chapter that provides benefits for prescription drugs may not require a participant in the group benefits program to purchase a prescription drug through a mail order program.
(b) Except as provided by Subsection (c), the board of trustees or a health benefit plan shall require that a participant who chooses to obtain a prescription drug through a retail pharmacy or other method other than by mail order pay a deductible, copayment, coinsurance, or other cost-sharing obligation to cover the additional cost of obtaining a prescription drug through that method rather than by mail order.

(c) The board of trustees or a health benefit plan may not require a participant who obtains a multiple-month supply of a prescription drug from a retail pharmacy under § 1560.003 to pay a deductible, copayment, coinsurance, or other cost-sharing obligation that differs from the amount the participant pays for a multiple-month supply of that drug through a mail order program.