They are allowed to operate inside of Maryland waters. I haven't sailed out of Baltimore since 2019, but it was open within a couple hours after we left port. I don't know when they shut down coming back, but, at the latest, they are required to close before they pass under the Francis Scott Key Bridge (closest Bridge to port).
https://www.baltimoresun.com/news/bs-xpm-1993-04-14-1993104066-story.html