You can call yourself a nation, but if the only reason you exist is the fact that the price of the fuel needed to ferry a police officer to your location and arrest you is more than what your country is worth, you're not a nation.
Micronations tend to be declared in spots where to do geographic and legal oddity, no larger jurisdiction actually applies.
If there's an entity already there, then the difference is split. You can't just extend your territorial jurisdiction and take over another country.
laughs in british
It's more than the cost of getting there.
Sealand can be "conquered" on a whim. It exists solely at the pleasure of the UK.