Possible Clues:

• Restricted zone
• Forbidden zone
• Cultivate oregano on edge of allotment? That's to be avoided!
• Prohibited zone
• Limited number are entering part of India that's out of bounds
• Rough end of California and Oregon a place to avoid
• Part of city off-limits
• District into which entry is dangerous or forbidden
• Region that's dangerous or to which entry is forbidden
• District that is barred to all or certain people