Off-limits (adjective)

Prohibited, not allowed or accessible.

Origin:

20th century: from off- + limit.

Examples:

1. The area was off-limits to visitors because of the dangerous wildlife.
2. The factory was off-limits to the public because of safety concerns.
3. The building was off-limits because it was under construction.
4. The beach was off-limits to swimming because of the strong currents.
5. The documents were off-limits to anyone without the proper clearance.