Where to enforce requirements

Requirement: the name variable in class X has a maximum length of 10 characters.

Should class X even know about this requirement, or should the requirement be enforced solely by the business logic class?

If I were to tell you what is wrong I would basically just be quoting your entire post. If you can't see what is wrong with it, then not only do you not understand OOP, but you don't know what you don't understand about OOP and that I fear is your downfall.