There are many tags relating to different topics .Suppose a person has answered questions relating to 4 different tags, the reputation must be split as
Tag1 rep =count1+
Tag2 rep =count2+
Tag3 rep =count3+
Tag4 rep =count4+
He must be given authority to cast a vote to close a question which has all these 4 tags (tag 1, tag2, tag3, tag4).
In this way high 'reputation' people who are irrelevant to a particular topic cannot close a question.
This simply prevents reputation misuse.