In the Mills v. Green case of 1895, the United States Supreme Court ruled that a writ of error becomes moot if it is not possible for the court to grant meaningful relief under any circumstances. The plaintiff, Mills, had sought to prevent an election from taking place in South Carolina on grounds that his rights were violated due to changes in voting qualifications which he believed were unconstitutional. However, by the time this case reached the Supreme Court, not only had that particular election taken place but also another one thereafter. Therefore, even if they agreed with Mills' arguments about unconstitutionality and violation of rights regarding those elections' procedures or outcomes - there was no practical remedy available since those events already occurred and couldn't be undone or redone differently retroactively; hence rendering his appeal as moot according to their judgment.

In the dissenting opinion for Mills v. Green, it was argued that the case should not have been dismissed as moot because there were still significant issues to be resolved. The main point of contention was whether or not a writ of error could be used to challenge an election result based on allegations of fraud and illegal voting practices. The dissenting justices believed that this question remained unanswered and therefore, the case should continue until a definitive ruling could be made. They also disagreed with the majority's assertion that since Mr. Mills had already taken his seat in Congress, any decision by the court would have no practical effect on him personally or professionally. According to them, if proven true, these allegations could potentially damage his reputation and future political career; hence they saw a clear need for resolution through legal means.