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?

>>19
I read it 5 times. Class X should be aware of this requirement, regardless of whether it's specified by documentation or a legacy database, as it is part of its internals. The GUI should have nothing to do with this logic, apart from enforcing a 10-character limit on input fields (having been told to do so by class X).