Over the years, people have filed a number of suits challenging the Senate filibuster rule — the rule that effectively means that much key legislation needs 60 votes to pass the Senate (not just a bare majority). The courts have not reached the merits in those cases, instead bumping them on various non-merits grounds such as a lack of standing. That happened again today in the D.C. Circuit in Common Cause v. Joseph Biden, Jr. The court said that the plaintiffs (the good-government group Common Cause and others) lacked standing because they had not sued defendants who could provide them relief that would redress their alleged injuries. They sued the Vice-President and three Senate functionaries. Why didn't the plaintiffs sue the Senators themselves or the Senate itself? As the D.C. Circuit explained, because a suit against those defendants likely would have been barred by the Constitution's Speech or Debate Clause.