TIL that NBA blackout policy (preventing people living to close to a team to see their matches on the NBA Live subscription) is a thing, how can this be legal?

Watched this random Youtube video: https://www.youtube.com/watch?v=P-TANCVoHlc

Basically a guy presenting some issues with modern technology.

And in the middle of it (around 9 minutes for people curious), I learn that apparently there is something such as "black out policies" for home games in your home town?

https://support.watch.nba.com/hc/en-us/articles/115002481154-League-Pass-Blackouts

How come that this can exist legally?