Capturing, seizing, or otherwise subduing a legendary Pokemon is a huge undertaking. It requires careful planning and preparation, tons of items, high-level Pokemon of many types, an iron will, and a brilliant strategic mind. In some cases, it can require additional manpower or even the help of another legendary Pokemon. These are apparently resources that Niantic has in spades, as they've managed to retake an Articuno that shouldn't have been in Ohio. That feat is, of course, much easier when the legendary Pokemon in question is a bit of data in the hit game Pokemon GO and you happen to be the company that operates the game. In any case, the ill-gotten legendary is now off the streets and no longer a looming shadow over local gyms.
For some background; earlier today, news broke that a Pokemon GO player, Kaitlyn Covey, had reported a glitch to Niantic and received a legendary Pokemon for her troubles. That was fishy enough in and of itself, since tons of bug reports hit Niantic's servers each day and until now, no legendary Pokemon had sprung up at local gyms or online. For that matter, nobody had even reported Niantic giving them any Pokemon at all for reporting bugs. The whole thing fell apart when Covey posted the letter, of course; poor grammar and misspellings betrayed a level of professional communication very far below the standard that a company like Niantic may be expected to adhere to. Nobody knew how Covey had actually gotten the Pokemon, whether through cheating or as the result of a glitch.
Putting the out of place Articuno up in a local gym to decimate other Pokemon and attract screenshots from slack-jawed trainers would have been bad enough, but Covey took to Twitch to make sure everybody who was interested knew that she held one of the three legendary birds. While Niantic would have eventually found out somehow, this pushed the process along significantly. While Covey's tale of how she got the Pokemon was an obvious lie, how it really happened was anybody's guess and may not have actually been cheating, so rather than banning her, Niantic simply called the Articuno back to its cage at Niantic's headquarters, where it will lie in wait with the three other birds, Mew and Mewtwo, and Ditto, until Niantic feels the time is right to let them loose on the world.