https://iaass.space-safety.org/wp-content/uploads/sites/24/2021/07/IAASS-near-space-the-quest-for-a-new-legal-frontier.pdf

Legally however, it is an indistinct region where it is not clear whether the operations that take place are covered by aviation or space conventions and treaties, in particular with reference to the freedom of overflight that applies to space orbital operations

Also:

Although outer space is free, if states are allowed to claim vertical sovereignty up to the point where orbital dynamics are possible, other states will be precluded from having free access to space

John A. Johnson, General Counsel of [NASA] and [of USAF], said in 1964 "there should therefore be no legal basis for protesting, merely on grounds of unpermitted presence, the overflight of national territory by ascending and descending spacecraft, regardless of altitude."

https://scholar.smu.edu/cgi/viewcontent.cgi?article=1126&context=jalc

Also see:

https://aviation.stackexchange.com/questions/43439/is-there-a-height-limit-to-national-airspace

https://en.wikipedia.org/wiki/Air_sovereignty

Posted by: JMW Turner |