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.
A child is not an adult, cannot consent to sexual activity, cannot enter into contracts. A child cannot, by definition, be a consenting adult. That is a completely separate issue from the government staying out of the sex lives of consenting adults.
On the Ginsberg article, got a cite? I've seen how these things get oversimplified in the retelling.