Consent, as defined by the laws in question, can not be given by a minor so it is automatically a statutory violation.
What? Of course consent can be given by a minor, rape isn't the same as sex with a minor who grants his permission. When you fuck with 15 yo with her approval it's not a rape, though it's still a crime.
PS. Well, at least that's how it works in EU, dunno about america.
A legally minor person (with no adulthood rights) can not consent to do something that is forbidden to them. 16 years old, 12 years old, 6 years old... they are all technically minor: if a 11yo girl tells you she wanted the dick, even if she really wanted it, its a rape still. We simply do not give minor the legal capacity to judge the situation themselves, as they are not considered mature/adult enough.
Then of course there is rape, and rape, but in both cases you face criminal charges, only the circumstances changes and can work toward a lesser or bigger punishment.
I'm sure different countries have different laws about sex and age, I know for example than in my country you can have sex with a minor if the age difference isnt above a few years (for example a 20yo male can have a 17yo girlfriend, and thats pretty normal when you think about it).
Also in some countries the age where you can have sex with anyone you want isnt the age where you reach adulthood and are legally responsible for your actions/can vote/can drink alcohool/etc... there is many grey areas around what laws permits you to do and starting at what age.