In other words, property owners are generally viewed as owning the airspace all the way up from their land, but that ownership does not confer any rights to restrict aviation, which is all done according to a separate body of federal regulations that has very little interest in land ownership. This is a similar situation to mineral rights, where land ownership matters more but there is still a separate system of regulations and deeds that operates largely independently from property title (which is why it's common in rural areas to buy land where the mineral rights are held by someone else).
Notably, though, this is all about flying - ground operations are different and you must have permission of the property owner for ground operations (except in emergencies when the regulations are generally tossed out the window for better glide). So property owners can restrict takeoff and landing, and (I think this is a little bit fuzzier legally but still generally agreed) remote operation of aircraft from their land.
There is no specific rule against flying even 1 foot above ground over someone else's property, though it's very unlikely that doing so would not violate other rules unrelated to airspace. These include operating a drone unsafely, violating laws against harassment, and photography in a context where someone would have a reasonable expectation of privacy.
