Brainy holds out his hand, which, she might note, has a nearly identical ring on it. Give it over. Now.

"Firstly, Legion flight rings are to only be issued to Legionnaires in good-standing--if you stole it from someone's desk, you're certainly not one. Secondly, it's likely you were abducted in transit, but considering the ring's capabilities, it may indeed be a "key" to getting back to our homes. However, it certainly won't be such a key in your hands. It must be properly analyzed by the engineering team. For both reasons, you are to relinquish it immediately."