American boaters take note: when inside the U.S. 3 mile territorial limit, the seacock at the through-hull must be turned to the "off" position, and secured in that position. The only time it may be open is if you're more than 3 miles offshore. Removing the handle from the seacock would constitute being "secured" and is accepted by the U.S. Coast Guard. Other acceptable ways of securing the seacock are wire and padlock, or non-releasing electrical wire ties, that must be cut off to be removed.
If you were to get boarded by the Coast Guard, and they find the seacock in the "open" position, there's a pretty hefty Federal fine!