Firstly, both parties are minors (under 18). That means they are under the care and control of their parents or guardians. If they engage in sex against their parents' wishes, their parents may take steps to stop them, including having them declared incorrigable, and possibly put in a juvenile facility.

Because neither is over 18 years, they are not liable under criminal law. However, the moment the 17 year old turns 18, he or she is liable for prosecution under A.R.S. § 13-1405 for having sex with a minor, even consentual.

It is a defense under A.R.S. § 13-1407 if the younger person is at least 15 years old, and the older person is less than 19 years or in high school, and is no more than 24 months older than the younger person.

If there are more than 24 months between the ages of the parties, and the older party turns 18 and is not in high school, that party can then be prosecuted for sexual conduct with a minor even if the younger party has turned 15. If the younger party is still 14, the older can be prosecuted.

This answer concerns only the likely legal problems of such sexual conduct. There remain the issues of possible unwanted pregnancy and sexually transmitted diseases, some of which cause lifelong need for treatment, and one of which is fatal.

If you have not considered the following, you should: When you have sex with one person, you are exposing yourself to all the persons that that person has had sex with, and all of the persons that all of those persons have had sex with, etc. That means that there may be lots and lots people whose health and habits you are exposing yourself to.

Both parties should consider carefully whether they want to begin a sexual relationship this early in their lives.

If you decide to do so, you should take precautions against the transmission of disease and against pregnancy. For more information on this topic, see the Arizona Planned Parenthood website.