I strongly urge you to reconsider what you are doing! Not only are you putting yourself at risk of a rape claim, but you really could assault someone. What he says is true. It is the law - the onus is on the party who initiates the activity to gain clear consent.

If that involves specifically asking, then so be it.

I see you've been downvoted to oblivion, which I hope gives you some idea as to how dangerous what you are saying is and how dimly most people are viewing it.