We consider a geodesic billiard system consisting of a complete Riemannian manifold and an obstacle submanifold with boundary at which the trajectories of the geodesic flow experience specular reflections. We show that if the geodesic billiard system is hyperbolic on its trapped set and the latter is compact and non-grazing the techniques for open hyperbolic systems developed by Dyatlov and Guillarmou [DG16] can be applied to a smooth model for the discontinuous flow defined by the non-grazing billiard trajectories. This allows us to obtain a meromorphic resolvent for the generator of the billiard flow. As an application we prove a meromorphic continuation of weighted zeta functions together with explicit residue formulae. In particular, our results apply to scattering by convex obstacles in the Euclidean plane. Contents 19 4.2. Smooth structure 19 4.3. Dependence of the model space on the Riemannian metric 21 5. Meromorphic continuation of the resolvent and weighted zeta function 23 5.1. Meromorphic continuation on open hyperbolic systems 23 5.2. A meromorphic resolvent for billiard systems 24 5.3. Application: meromorphic continuation of Z f 27 References 29