@benhamill The Strait Dope covered this in 2015, for another opinion. TL;DR: no established law.

https://www.straightdope.com/21344309/do-property-lines-extend-to-the-center-of-the-earth

The question's come up in several contexts.

#RuleOfCapture is a #CommonLaw (case law) doctrine which arose from wild game but which came to be applied to mineral rights, notably water, oil, and gas. It's ... really bad law, IMO, but still serves as precedent.

Mineral rights played a role in the Iraq-Kuwait War of 1992, in which Iraq claimed Kuwait was tapping oil reservoirs within Iraq's borders.

It's also been mooted in the context of carbon capture:
https://www.cambridge.org/core/journals/international-and-comparative-law-quarterly/article/abs/digging-deep-property-rights-in-subterranean-space-and-the-challenge-of-carbon-capture-and-storage/408416F3ACB16666E74AF08B1D6D17DD

It's worth recognising that much law is based on 1) experienced conflicts and 2) effectual enforcement ability. Maritime territorial waters came to be defined largely by the effective range of shore-based cannon. Five-mile guns -> five-mile law. 20-mile guns -> 20 mile law. 200 miles isn't the outer bound of radar and fighter aircraft or missiles, but does reflect a reasonable limit for same. Note that the US claims airspace (and transit fees) for much of the Pacific Ocean AFAIR.

#PropertyRights #SovereignTerritory #SubterraneanRights #MineralRights #Law