  We consider an inverse problem for a radiative transport equation (RTE) in
which boundary sources and measurements are restricted to a single subset $E$
of the boundary of the domain $\Omega$. We show that this problem can be solved
globally if the restriction of the X-ray transform to lines through $E$ is
invertible on $\Omega$. In particular, if $\Omega$ is strictly convex, we show
that this local data problem can be solved globally whenever $E$ is an open
subset of the boundary. The proof relies on isolation and analysis of the
second term in the collision expansion for solutions to the RTE, essentially
considering light which scatters exactly once inside the domain.
