  Observables in gravitational systems must be non-local so as to be invariant
under diffeomorphism gauge transformations. But at the classical level some
such observables can nevertheless satisfy an exact form of microcausality. This
property is conjectured to remain true at all orders in the semiclassical
expansion, though with limitations at finite $\hbar$ or $\ell_{Planck}$. We
also discuss related issues concerning observables in black hole spacetimes and
comment on the senses in which they do and do not experience the form of chaos
identified by Shenker and Stanford. In particular, in contrast to the situation
in a reflecting cavity, this chaos does not afflict observables naturally
associated with Hawking radiation for evaporating black holes.
