There is a very important distinction between airspace and plain space. Violation of a country's airspace is a wilful act (unless of course you're lost). But yo

There is a very important distinction between airspace and plain space. Violation of a country's airspace is a wilful act (unless of course you're lost). But you will inevitably have to fly over another country if you want to be in orbit. Even geosynchronous slots are limited to the equator (GSO insertion also requires phasing). This doesn't prevent countries from claiming 'aerospace' and destroying invading crafts. However, other countries could do the same and space exploration will be a non-starter for humanity as a whole. This is probably the reason why countries agreed to space treaties allowing overflight - and it will probably remain the same. Of course, this logic doesn't apply to suborbital flights. Any country with the means will probably just shoot down unauthorized objects on suborbital trajectory into their airspace.