The paper considers impulsive control systems, where the evolution equation depends linearly on the time derivatives of the control function. The basic theory of "graph completions" is here extended to control functions in feedback form. In the case where the control u=u(t,x) is piecewise smooth, with a jump along a hypersurface Σ in the t-x space, results are proved on the existence and uniqueness of solutions, and on their approximation by means of smooth feedbacks. The paper is concluded with a couple of examples, concerning the feedback control of mechanical systems by means of active constraints.