Miss. Code § 25-15-13
Each eligible employee may participate in the plan by signing up for the plan at the time of employment. Each eligible employee who declines coverage under the plan must sign a waiver of coverage. After acceptance in the plan, the employee may cease his or her participation by filing a specific disclaimer with the board. Forms for this purpose shall be prescribed and issued by the board. All eligible employees will be eligible to participate in the plan on the effective date of the plan or on the date on which they are employed by the state, whichever is later, provided they make the necessary contributions as provided in this article. Spouses of employees, unmarried dependent children from birth to age nineteen (19) years, unmarried dependent children who are full-time students up to age twenty-five (25) years, and children with physical or mental disabilities, regardless of age, are eligible under the plan as of the date the employee becomes eligible. If both spouses are eligible employees who participate in the plan, the benefits shall apply individually to each spouse by virtue of his or her participation in the plan. If those spouses also have one or more eligible dependents participating in the plan, the cost of their dependents shall be calculated at a special family plan rate. The cost for participation by the dependents shall be paid by the spouse who elects to carry such dependents under his or her coverage.
Miss. Code § 25-15-13