[Troubleman23]

Now I just thought of this because in the past this has happened but I would just let it slide, But Arkmer's Engagement Strike 13 says as soon as a figure becomes adjacent to him you roll the d20 to see if you inflict a wound. There are many abilities like this out there and whenever some of my friends move their figs. adjacent to one of mine with that sort of ability they say "Oh can I redo my turn then?" I usually let it slide but it doesn't seem fair they moved into a trap and shouldn't be able to weasel their way around it. So what would the official ruling be of this?