>https://www.govinfo.gov/app/details/CFR-2011-title5-vol1/CFR-2011-title5-vol1-part351/context
351.806 Status during notice period.
When possible, the agency shall re-
tain the employee on active duty sta-
tus during the notice period. When in
an emergency the agency lacks work or
funds for all or part of the notice pe-
riod, it may place the employee on an-
nual leave with or without his or her
consent, or leave without pay with his
or her consent, or in a nonpay status
without his or her consent.
That's the only "emergency" I found in that document