  Nonlocal gravity (NLG) is a classical nonlocal generalization of Einstein's
theory of gravitation based on a certain analogy with the nonlocal
electrodynamics of media. The history dependence enters NLG through a
constitutive relation involving a causal kernel that should ultimately be
determined via observational data. The purpose of this paper is to reformulate
nonlocal gravity such that the nonlocal aspect of the constitutive relation
directly connects measurable quantities as in the nonlocal electrodynamics of
media. The resulting constitutive relation turns out to coincide with the
recent suggestion of Puetzfeld, Obukhov, and Hehl [25]. With the new
constitutive relation of NLG, it is possible to show that de Sitter spacetime
is not a solution of NLG.
