In this pic, the cable has a ramp cover (good) but it isn't secured (bad). Sidewalks are for everyone—blind people, wheelchair users, people who can't lift their feet up very high, small kids, people using rolling carts and suitcases, etc etc. If the cord was secured in such a way that all of those people were not impeded, then it would be okay IMO. But you may still need to check municipal codes.