It is proposed that spacetime is not the most proper space to describe
metamaterials with nonlocality. Instead, we show that the most general
and suitable configuration space for doing electromagnetic theory in
nonlocal domains is a proper function-space infinite-dimensional
(Sobolev) vector bundle, a special case of the general topological
structure known as fiber bundles. It appears that this generalized space
explains why nonlocal metamaterials cannot have unique EM boundary
conditions at interfaces involving spatially dispersive media.