Whew, why does he want to do this, for himself, or because he knows the child and thinks she is being abandoned or is in a dire position needs help?
In his shoes first I would talk to a lawyer, and have the lawyer review the agreement signed at the time of surrendering parental rights, to see if on the face of it or by implication it says your friend would never contact the child. (I mean, that is what surrendering parental rights is supposed to do. The people who take on the child are given the assurance that the parent won't pop up later and want to take over the kid they went to so much work to raise.) The lawyer can also explain what the law says about this; the last thing your friend needs is a protection order filed against him, and that could happen!
Also, I would suggest the friend talk to a counselor specializing in family relationships. Age 14 is very young to suddenly get this news, especially since (unless he knows her peripherally already) he is a stranger and intends to tell her that her own mother, who she loves and trusts, has not revealed all. If his intention is to ruin the mother's life or make the child think "why didn't my mom tell me?" that is an intention worth reconsidering. Even if it were legal, it is unkind to just unilaterally violate the intention of a surrender of parental rights. I mean, not kind to the kid especially.
If the purpose of his declaration of fatherhood is that he knows the child from a distance and thinks she is being neglected or having a hard life, that is one thing. But if it's just for his own pleasure in getting to be a father, he might consider waiting until the child is 21 or more. His pleasure is not the important thing here, and for 14 years, someone else has been doing the hard work of raising the child. It's kind of sly to just skate up and ask for credit after so much hard work is done by someone else.
I'd definitely talk over all of this with the family counselor and if the situation seems to merit some kind of approach to the child, I'd also have a meeting with the counselor and the child's mother (or whomever has been raising her) before talking to the child. At the least, the child deserves for the people she loves and trusts the most to be the ones who tell her the news, if it seems like a good idea for her to know at all, at this young age.
In short, in answer to your last question/sentence above, it seems very possible that he does not have the legal right to do this and could be subject to lawsuit if he does. It seems pretty sure that he doesn't have the right while she is still a minor. He should definitely get legal advice, and also re-think the damage he could do to her.