Despite being claimed by the United States, Canada maintains its ownership with a presence on this disputed island including establishing rules that protect the puffins and other nesting seabird.
Machias Seal Island (Wikipedia)
In 1918, with Canadian agreement, a small detachment of Marines was placed on the island following the U.S. entry into the First World War, as a means to assist in protecting the territory and its key lighthouse guarding the entrance to the Bay of Fundy from German U-boat attack. These forces were withdrawn after several months, and no U.S. presence has been re-established since. Several private citizens in Maine have staked ownership claims of the island, and American tour boat operators from Jonesport and Cutler bringing tourists to view seabirds have maintained their sovereignty in light of some Canadian conservation measures in the seabird sanctuary, such as removing a wharf (slip), and limits to visitors during sensitive periods for birds. Several skirmishes have arisen over lobster fishing rights in recent decades.
Quotes and photos are from Wikipedia.