What is the principle that children can consent to other children of the same age, but not to an adult, called?

Question

Two three year old children that agree on "playing doctor" and examining each others bodies, including genitalia are not committing a crime (but if one three year old child forces another three year old it is a crime, although it will be a case for the parents/psychologist/school counsellor not the police). Two 13 year old children/adolescents that consent to have sex are not committing a crime (there are some weird exceptions, particularly in America, where holding a nude photo of yourself is considered child pornography but that is an exception). Furthermore, two 13 year olds can enter a contract if it is "reasonable" for their age, e.g., maybe €/$ 30-50 or so.

However, if one party in all those situations was 25, it would be illegal because children can't consent or enter binding contracts with an adult (for substantial amounts of money).

Is the principle described above called something? How old is it? Did the Romans apply a similar concept? The medieval Catholic church?

Answer 1

The exception is often called a Romeo and Juliet exception colloquially when applied to statutory rape laws. See, e.g. here. It is an exception to the age of capacity to consent to sexual conduct, not an exception to the capacity to consent to a contract.

When children are very young (typically in the range of 7 to 12 as set by statute of common law, it is 6 in North Carolina) they lack the capacity to commit a crime, which has to do with the age of the offender and not the mutual ages of those involved.

Is the principle described above called something? How old is it? Did the Romans apply a similar concept? The medieval Catholic church?

The principle that you described is a misunderstanding of the law and is incorrect. No jurisdiction has adopted it in the sense that you articulate. When these instances are not punishable as crimes they are not punishable for different reasons. So, the question of "how old is it?" is a category error that has no answer.

The medieval Catholic church did not have any criminal or contract jurisprudence. Both of those domains were handled by secular officials, usually either feudal lords or the officials of a "free city". In the medieval period, feudal secular law was often arbitrary and often came down to the personal whims of the individual holding the title. As @hmvsm appropriately notes, however, it did have doctrine about when a child was morally responsible for sins, but final adjudication of whether you sinned or not was ultimately determined in the afterlife, and the church doctrine of forgiveness of sins made the issue moot to a great extent.

The Roman Empire, of course, did have secular laws, but its laws in the area of contractual capacity, which are largely replicated by modern European civil codes, didn't contain the principle that you propose. To the best of my knowledge, the modern concept of statutory rape was unknown in the Roman world. The lack of hard age based cutoffs was, in part, because vital statistics record keeping was nowhere near universal, so many people did not even know their exact age in a legally provable manner. Approximate age in the very late Roman Empire would often have been determined based upon time elapsed since an infant baptism as recorded by church officials, but Christianity went from being very rare to universal between about 275 CE and 450 CE, and Rome fell not long after that point.

Answer 2

 What is the principle that children can consent to other children of the same age, but not to an adult, called?

england-and-wales

There isn't one, per se.  A child can enter into a contract with an adult - for example by buying sweets, getting a bus ticket, or having a part-time job.

Two three year old children that agree on "playing doctor" and examining each others bodies, including genitalia are not committing a crime (but if one three year old child forces another three year old it is a crime, although it will be a case for the parents/psychologist/school counsellor not the police). 

The age of criminal responsibility is 10 so they do not, and cannot, commit an offence even in the circumstances described in the parenthesis. However there may well be the need a safeguarding intervention by Social Services etc to manage any potential risks if they are displaying sexualized and / or violent behaviour at such a young age.

Two 13 year old children/adolescents that consent to have sex are not committing a crime ... Furthermore, two 13 year olds can enter a contract if it is "reasonable" for their age, e.g., maybe €/$ 30-50 or so.

Notwithstanding the "Romeo and Juliet" scenario (and whether or not any action would actually be taken by the police), they both commit an offence - s.9 Sexual Activity with a Child or s.2 Assult by Penetration for example. The former by virtue of s.13.

Furthermore, the offence under s.47 Paying for Sexual Services of a Child would make any such contract void as being unlawful regardless of the amount of payment or the payer's age (if 10+).

However, if one party in all those situations was 25, it would be illegal because children can't consent or enter binding contracts with an adult (for substantial amounts of money).

Again, a child can enter in to a contract, but the 25 year old's "contract" is an offence under s.47 so will be void - as well as committing a host of other offences under the 2003 Act.

Answer 3

In your first example this is a result of what's known as "Age of Criminal Liability" which is the minimum age one must be in order for the person to be held criminally liable for breeches of law (It depends on the jurisdiction in question, but typically 11 years old is the extreme high of the age while 7 is often the low end of the range.). Two three year olds would not be criminally liable because they aren't developed enough to know better and thus shouldn't be jailed.

The second example is called a "Romeo and Juliet Exemption" and generally permits teens who are relatively similar in age who engage in sexual behavior to not be guilty of statutory rape charges so long as 1.) Both parties are consenting. 2.) Neither party is in a trusted position of authority over the other (i.e. a Student Coach and a team member or Student Teacher with a Student) 3.) Neither is below a certain hard minimum age (usually 11). The law is designed to prevent situations where one teen might be over "Age of Consent" but the other is not, even though they share a birth year. There is room for age difference, but it's not absolute (there usually is a point where courts will say the gap is too wide). Typically this is a protection enjoyed by the older partner in the relationship, as he/she will be the one who would have issues with a relationship with the younger partner.

I'm not sure on the nuances of Child Law contracts, but typically a parent or legal guardian may sign for a child under 18 unless said child is emancipated at a younger age, which requires a court order.

Roman Law likely did not have similar age concerns as back when it existed, the age of adulthood was much lower (13 was typically an adult age, and you could certainly marry someone at that age) and the rights such as consent were not like to today's standards. The patriarch of a household could have his children killed if he so desired.

I can attest that the Catholic Church did and still does hold true to that very young children cannot commit sins, since all sins must be committed with the knowledge that they are sinful. Typically the sacrament of Reconciliation (which is all about admitting to one's sins to receive forgiveness from them) is typically first given to someone when they are 7 to 8 if they are raised in the faith (The sacrament of Baptism covers Original Sin).