22 CFR §51.63

1. (a)The Secretary may restrict the use of a passport for travel to or use in a country or area which the Secretary has determined is:
   1. (1)A country with which the United States is at war; or
   2. (2)A country or area where armed hostilities are in progress; or
   3. (3)A country or area in which there is imminent danger to the public health or physical safety of United States travelers.
2. (b)Any determination made and restriction imposed under paragraph (a) of this section, or any extension or revocation of the restriction, shall be published in the Federal Register.
3. (c)A passport may not be designated as valid only for travel to Israel.