The notice requirement is found in
29 CFR2590.701-6©QUOTE
© Notice of enrollment rights. On or before the time an employee
is offered the opportunity to enroll in a group health plan, the plan is
required to provide the employee with a description of the plan's
special enrollment rules under this section. For this purpose, the plan
may use the following model description of the special enrollment rules
under this section:
If you are declining enrollment for yourself or your dependents
(including your spouse) because of other health insurance coverage, you
may in the future be able to enroll yourself or your dependents in this
plan, provided that you request enrollment within 30 days after your
other coverage ends. In addition, if you have a new dependent as a
result of marriage, birth, adoption, or placement for adoption, you may
be able to enroll yourself and your dependents, provided that you
request enrollment within 30 days after the marriage, birth, adoption,
or placement for adoption.