Boston’s top cop wants drones hovering over next year’s marathon, but getting his hands on one may be easier said than done. More than 30 states, including Massachusetts, are rushing to restrict the use of drones by law enforcement, with some seeking to ban it in all but the most extreme circumstances. Even if unmanned aerial systems could have shortened the search for the terrorists who wreaked havoc on Boston last week, many people are deeply skeptical about giving authorities carte blanche to use potentially dangerous technology. “It’s not surprising that you have law enforcement agencies rushing out to use...