Legal Question in Criminal Law in California

The state does what it does regardless of how anybody else feels about it. You are just as much at risk in one state as the other, going from state to state just increases the theoretical number of crimes you could be charged with (e.g. transporting women across state lines for licentious purposes, the Mann Act). It is not my role to tell you how to break the law. Have a great time in Vegas and don't do the nasty until she turns 18. In the unlikely event that you are visited by the police, say nothing at all and ask for a lawyer.

You are committing a crime every time you and your fiancee have sex in California. That will be true until she turns 18, unless the two of you get married first. (Parents can authorize their teens to marry before reaching 18, but it rarely happens.)

I am not a Nevada lawyer, and you may want to run your question by someone who is. But I just did a little research and it seems that the age of consent in Nevada is only 16. (There are a number of wrinkles to Nevada law on this point, but it doesn't seem that any of them apply to you.) If I'm right about that, then you would not be committing a crime if you and she had sex in Nevada. Of course, that doesn't mean it's a good idea.

Even in California, "somebody reporting that they believe she has been sexually active with an adult" would not be enough to get you prosecuted or convicted. People "believe" all sorts of things. In order to convict you, the prosecutor would have to prove a *specific* incident of sexual contact beyond a reasonable doubt. A witness who merely "believes" the two of you are having sex could not remotely satisfy this requirement. But if she has a solid basis for her belief, she may be able to give the authorities enough evidence to begin a case against you.

I strongly suggest that you and your girlfriend stop having sex in California until she is 18. If you are convicted of having sex with her, you will likely have to register as a sex offender for the rest of your life. Registered sex offenders have very bleak futures to look forward to. You will also likely spend some time behind bars, where the other inmates tend to be quite unkind to men convicted of having sex with minors.

Unfortunately in California there is absolutely no way around this law. It is a 100% liability crime. In California the problem is if one person is over 18 years old and the other person is not yet 18, and they have consensual sex the crime has occurred. There is absolutely no wiggle room and no way around it. Consent is not an issue, and her parents current knowledge and apparent current consent does not matter. They can always change their minds. Furthermore, anyone can report the incident and if Law Enforcement wants to investigate they will. If they find proof that sex occurred between someone 18 years old or older and someone who was not yet 18 years old they will prosecute. The idea behind the law was good, however the way the law is written and the way it is enforced is very poor. The problem always occurs when the boyfriend is a couple of months older than the girlfriend and they start having a sexual relationship prior to his turning 18. After he turns 18 they continue their relationship in the same exact manner and then he gets arrested and charged with a crime. I have seen many incidents where this law has destroyed someone's future because Law Enforcement and the District Attorneys did not use common sense.

I do not know the law in Nevada. Not all states use 18 years as the age of majority for the purposes of statutory rape. California does. You might want to ask a Nevada attorney for an opinion.