Jack's eyebrows might have shot into his hairline, but he didn't really care. His arm wrapped around her in response to the kiss. He wouldn't force her to stay close, but he was still pulling her closer all the same as the kiss was returned with vigor.
He didn't understand it, really, but for now he wouldn't question it. If she realized that he might not end up working with the League and she'd still kissed him, then that was just fine with him.