If a person purchases an oil platform in the deep waters of the ocean, can that property be legally declared its own country?

Apparently (e.g.. Sealand), but it also has to be continously inhabited, have its own currency & constitution, etc. Plus, you have to avoid claims from existing nations.

Well, ‘legally’ would depend on the country—and if you’re independent of any country, what’s legal is up to you. On the other hand, if you’re independent of a country, you’re independent of their defense ministry, so you’ll have to do your own law enforcement. Sealand is a good example of the sweet spot, here: independent, but so boring they’ll never get any trouble for it.

I think somebody tried to do that with a half-submerged reef that was in international waters. As soon as they built something, Tonga or some such nearby nation annexed it, and the rest of the world didn’t say “boo” to stop them.

Note the British court determined Sealand was not under British jurisdiction because it was located in international waters. It did NOT hold Sealand was a sovereign nation. Sealand has gotten by because it hasn’t been worth anyone’s time to push the issue. As pointed out above, not being part of a sovereign nation also means you don’t get the associated benefits.

If the issue was pushed in a court, I believe they would find Sealand or your hypothetical “installation” to not be a sovereignty, but rather personal property or a fixture to international waters and land. Therefore, international admiralty law would apply. I find it interesting evidently Sealand can’t keep the peace in a population of a dozen or so, any better than any country can.

If there was ever any really serious illegal activity going at Sealand, I am sure the British government would not hesitate to just take it. In fact, it might not even be too difficult to get a court decision declaring the “residents” of Sealand to be pirates, or at the most, squatters. Who is going to complain? The United Nations?

A very interesting related issue is that the recent thawing of the Arctic ice cap, if it continues, will finally make a Northwest Passage above North America and Asia a viable sea route, which will not only shave huge margins off long distance shipping costs, but may also finally make access to the far northern oil, gold, uranium and other resources practical. The U.S., Russia, Canada and a number of other countries are already starting to duke it out, using legal arguments resting on centuries old explorations, submarine expeditions under the polar ice cap, et cetera. Should be fun to watch.

there is a oil platform I think it is off the spanish coast and it is it’s own country they deliver servers by helicopter to the platform I saw pictures of it years ago but can’t remember the name of it they protect it from invasion and someone tried to shut them down but I don’t think they ever did——if anyone has the info please post thanks