"Ground of" is a wrong idiom.
"of violating" and "for allowing" are wordy and awkward phrases. Keeping both in mind we can eliminate options A and B.
The pronoun "their" in option B is ambiguous because there's no logical plural noun for it to refer to, but "it" can logically refer to "the ban." The pronoun "it" isn't ambiguous here in option C and D; it refers to "the ban" unambiguously.
In C, “violates” is
...
"of violating" and "for allowing" are wordy and awkward phrases. Keeping both in mind we can eliminate options A and B.
The pronoun "their" in option B is ambiguous because there's no logical plural noun for it to refer to, but "it" can logically refer to "the ban." The pronoun "it" isn't ambiguous here in option C and D; it refers to "the ban" unambiguously.
In C, “violates” is
...
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