I have to agree that I think calling the police sounds a little drastic - but if this adult is pursuing your 14 year old daughter in an inappropriate manner, and won't take the hint when she is told, "please back off", then maybe something a little more firm is needed. However, I think you'll be surprised how many 14 year olds think it's cool to have much older friends. I think you need a serious conversation with your daughter about why this concerns you so much - there are a lot of kids of that age who hang around with older "friends" so that they can get into bars illegally as one of them. Even if this is not sexual in nature, then there is at least one serious underlying issue that needs to be addressed. You need to know who's leading who on, why, and get all of the facts straight before you ring the police. You really need to be absolutely certain that what is going on is sinister.
On the other hand, I can understand why you need to do what you must, especially if your daughter is 14 - she is a minor, of course. She's also probably at that age where she is very difficult to talk to. You're probably right, this should be nipped in the bud before it does become something other than innocent fun, if that is what it is just now. But it needs to be handled in such a way that your daughter isn't going to feel betrayed or that you restrict her activites too much. It's a delicate situation from what I can tell.
Anyway, I have my opinions, but I don't have the facts and am not experiencing it the way you are. I really hope you can come to an agreeable solution for everybody
it'll get better