Svalbard allows anyone in who can prove they can support themselves due to a long standing international treaty.

However that's the thing: the real problem with unrestricted migration is it'll overwhelm social safety nets. Svalbard is ensuring that won't happen with that policy, and the fact it's a freezing cold place in the Arctic that few want to move to.

are there any historical examples of this?

it does seem more likely to happen moving forward as the total pool of immigrants available around the world declines.