When it doesn't comply with the rules governing the Roman numeral system.
They are an invalid arrangement of Roman numerals
This arrangement of Roman numerals is invalid
They are an invalid arrangement of Roman numerals.
It is an invalid arrangement of Roman numerals
As a Roman numeral it has no equivalent and therefore it is invalid.
They are an invalid arrangement of Roman numerals
This arrangement of Roman numerals is invalid
No it is invalid
They are an invalid arrangement of Roman numerals.
It is an invalid arrangement of Roman numerals
As a Roman numeral it has no equivalent and therefore it is invalid.
They are an invalid arrangement of Roman numerals
Meaningless because they are an invalid arrangement of Roman numerals.
It does not exist because they are an invalid arrangement of Roman numerals
None because they are an invalid arrangement of Roman numerals
As Roman numerals they are invalid because they do not conform with the rules governing the Roman numeral system.
No equivalent is possible because they are an invalid arrangement of Roman numerals.