Catalysis of the reactions: H2O + N(omega)-(ADP-D-ribosyl)-L-arginyl- = ADP-D-ribose + L-arginyl-, and H2O + N(omega)-(ADP-D-ribosyl)-L-arginine = ADP-D-ribose + L-arginine.
nomega-(ADP-D-ribosyl)-L-arginine ADP-ribosylhydrolase activity