5 USC 8702 - Automatic coverage

(a) An employee is automatically insured on the date he becomes eligible for insurance and each policy of insurance purchased by the Office of Personnel Management under this chapter shall provide for that automatic coverage.
(b) An employee desiring not to be insured shall give written notice to his employing office on a form prescribed by the Office. If the notice is received before he has become insured, he shall not be insured. If the notice is received after he has become insured, his insurance stops at the end of the pay period in which the notice is received.
(c) Notwithstanding a notice previously given under subsection (b), an employee who is deployed in support of a contingency operation (as that term is defined in section 101 (a)(13) of title 10) or an employee of the Department of Defense who is designated as an emergency essential employee under section 1580 of title 10 shall be insured if the employee, within 60 days after the date of notification of deployment or designation, elects to be insured under a policy of insurance under this chapter. An election under the preceding sentence shall be effective when provided to the Office in writing, in the form prescribed by the Office, within such 60-day period.