exclusion zone
noun /ɪkˈskluːʒn zəʊn/
  /ɪkˈskluːʒn zəʊn/
 - an area where people are not allowed to enter because it is dangerous or is used for secret activities
- Armed forces have set up an exclusion zone around the island.
 - An enemy plane was shot down after it violated the exclusion zone.