16 U.S.C. § 440 — Closure in times of national emergency

This section gives the Secretary of the Interior emergency power over Fort McHenry. If a national emergency happens, the Secretary may close Fort McHenry. While it's closed, the fort may be used for any and all military purposes. That military use can continue not just during the emergency itself, but also for some time afterward — for as long as the public's needs require it. The law does not set a fixed length for that extra period; it leaves that judgment open, tied to actual public need. In other words, this section puts the decision to close the fort, and the decision on how long military use continues afterward, in the Secretary's hands.