Åland must not be fortified and the right to a military presence within the demilitarised zone is strictly limited. Neutralisation is defined by Åland remaining neutral during all wartime operations.
Convention on the Demilitarization of the Åland Islands, 1856:
“… the Åland Islands shall not be fortified and that no military nor naval establishment shall be maintained or established there.”
Convention on the Non-Fortification and Neutralisation of the Åland Islands, 1921