half guard no gi

when playing half guard without gi, I face difficulties when the opp pass his right arm under my left leg and put his hand on my right thigh (I have his right leg in my half guard), and try to pass from there. I think to play the quarter guard, (and try to roll under the opp to get the omoplata on his right arm for example), but for me it's harder without gi, especially because it his harder to control his right arm when I can not grab his sleeve.
What do you guys like to do in this situation ? Thanks

Does he have his arm hooking around the bottom of your leg? If so, try to take his back. Just the threat of it may be enough to get him to abandon his pass.