[arcticbull]

Same as if there was a medical emergency anywhere along the flight path. The plane pulls into the nearest gate where you'd be looked after and you get off. The prohibition is on transporting passengers between two domestic points as a single flight or as a single ticket / with stops under 24h - but note that there's nothing to stop you for instance buying a ticket from SFO-NRT and then a separate NRT-GUM ticket both on ANA.

Cabotage is also referred to as the 9th air freedom, for the curious. [1]

The prohibition on cabotage also applies to passenger and cargo ships. [2]

[1] https://en.wikipedia.org/wiki/Freedoms_of_the_air

[2] https://en.wikipedia.org/wiki/Cabotage