Cuius est solum eius est usque ad coelum et ad inferos

I chose today's phrase for one reason: As someone with no background in Latin, this phrase gave me fits the first time I came across it in property law (in my defense, part of the problem was that Justice Brandeis used a different phrasing). We don't need to recap how much time I spent parsing it down to finally come up with the correct definition (let's just say that, somewhere in my property notes sits a handwritten page with each word and all its possible meanings followed by a rubric to assemble the most likely translation). Figuring it out made filled me with an undeserved sense of accomplishment. It also made me wish there was an Idiot's Guide to Law Latin.

Cuius est solum eius est usque ad coelum et ad inferos
Or, as used by Justice Brandeis: Ab orco usque ad coelum
The definition I eventually cobbled together: from the underworld all the way to heaven
Wikipedia's more precise definition: "for whomever owns the soil, it is theirs up to the sky and down to the depths."

The phrase has a long history, dating to either the Roman Empire or the English Common law system (I found references to both in my research). The phrase is mostly seen in property law, but it will also pop up in air and space law (usually as the shortened usque ad coelum). In short, it defines the extend of a property owner's rights in the land. The American legal system adopted the theory as espoused by Blackstone, giving property owners unlimited control over the space above and the earth below their land. One early American case to reference this theory was State v. David, 1 Del. Cas. 160 (1797), which declared a landowner the possessor of a barrel of fish buried on his property.

My own initial exposure to the phrase was in Pennsylvania Coal Co. v. Mahon, 260 U.S. 393 (1922), specifically the dissent written by Justice Brandeis. The case itself dealt with the divide between surface and subsurface property rights, and, while Brandeis' dissent uses the phrase, it is secondary to an analysis of the relationship between police powers and property ownership.

The numerous technological breakthroughs of the past 100+ years have significantly curtailed the traditional American application of the doctrine. This is especially true regarding air and space law, although subsurface rights are more complex. Depending on the issue (e.g., groundwater or mineral rights), the application of the theory differs.

Bottom line? The phrase (and the likely variations) remain in use today, even if the theory itself is no longer as absolute as Blackstone claimed.

Some other variations on the phrase:
centro usque ad coelum
cujus est solum, ejus est usque ad coelum et ad inferos

Consulted sources
Jesse Dukeminier et al., Property (6th ed. 2006).
Malcolm N. Shaw, International Law (5th ed. 2003).
John G. Sprankling, Owning the Center of the Earth, 55 UCLA L. Rev. 979 (2008).