  Given three transversal and sufficiently regular hypersurfaces in R^3 it
follows from work of Bennett-Carbery-Wright that the convolution of two L^2
functions supported of the first and second hypersurface, respectively, can be
restricted to an L^2 function on the third hypersurface, which can be
considered as a nonlinear version of the Loomis-Whitney inequality. We
generalize this result to a class of C^{1,beta} hypersurfaces in R^3, under
scaleable assumptions. The resulting uniform L^2 estimate has applications to
nonlinear dispersive equations.
