Established in English common law
Easement by necessity (common law)
When a landowner sells off a parcel that ends up with no road access, courts have long granted the buyer a right to cross a neighbor's land, an "easement by necessity," so the land is not unusable.
Then
Landlocked parcels became developable by crossing an adjacent owner's property.
Now
The doctrine underpins modern city rules that let non-frontage lots be built under public oversight.
Why this matters now
Alexandria's special use permit is the city's formal version of this: a way to make a lot with no street frontage buildable, decided in public rather than left to private agreement alone.