What can a parent of 16 yr old girl do to protect her sexually from 18 yr old boy she likes. UTAH?

Unfortunately, not much. Your daughter is 16, which means that she can consent to sexual activity without your approval. There would be no cause for statutory rape either, because there is not more than three year's difference in their ages. The most you can do is talk with your daughter about the issue, and explain your position on premarital sex (it seems like her having sex is what is upsetting to you). Legally, though, you cannot stop her or bring charges against him.

Well if you know they are having sex you can always have him arrested for statitory rape. talk to the boys parents.