In Common Lisp the arglist is not a runtime datastructure, unless one uses something like APPLY. This means that the usual implementation (compiler/interpreter)

In Common Lisp the arglist is not a runtime datastructure, unless one uses something like APPLY. This means that the usual implementation (compiler/interpreter) will check the declared keyword arguments: is it duplicate, is it used, ...? For calls it can be checked if the keyword is known. That's usually all done by default.