Is it the government's place to regulate those actions?
Yes. That is rape. Thank you for the easiest question in this thread.
But thanks to the Lawrence decision, perhaps it is not such an easy question. Lawrence was the first step on a slippery slope that could eventually overturn any state laws against incest, polygamy, and possibly even pedophilia. Bader-Ginsburg is on record that statutory rape laws and age of consent laws are discriminatory and should be abolished. So, when those laws start getting challenged on a "privacy" or "discrimination" question, then the "statutory rape" status of the action is called into question. Is it STILL the government's place to regulate (or prohibit) those actions.