  The imaging of Sagittarius A* (Sgr A*) and the supermassive black hole at the
center of Messier 87 (M87*) by the Event Horizon Telescope constrains the
location and nature of emission from these objects. Coupled with flux limits
from the near-infrared through the ultraviolet, the attendant size constraints
provide strong evidence for the absence of an accretion-powered photosphere,
and therefore for the existence of an event horizon about an astrophysical
black hole. Here, we demonstrate that a broad class of naked singularities are
also generically excluded, regardless of the nature and unknown physical impact
of singularity itself, subject to a single weak assumption about locality.
While we restrict our attention to static, spherically symmetric spacetimes, we
are nevertheless able to exclude a large number of commonly invoked naked
singularity spacetimes in this way.
