That's not how logic works. You just said: X is not in A. X is in B. Therefore, if X were in A, A would not go to B. This is not a valid syllogistic form. For example, here is an argument of the same structure: Guns are not allowed in school. Guns ar
The beauty about Ursula is that she held up her part of the bargain, gave Ariel 3 days to kiss the Prince. Nowhere did Ursula say she could not interfere. It reflects how real life contracts work... Student loans for example.