The judge argues that the petitioners did not have standing to sue (it was brought by Common Cause), and the courts would violated the separation of powers doctrine if it were to intrude on what it sees as an internal issue within the Senate.
The decision can be found here.
From ScotusBlog:
Ruling that the courts have no power to do anything about it, a federal judge on Friday threw out a claim that Senate filibusters are an unconstitutional denial of majority rule. U.S. District Judge Emmet G. Sullivan, in a forty-seven-page opinion, said none of the challengers had a right to pursue their case in court, and ruled that it would intrude on the Senate’s powers for the court to decide “an important and controversial issue.”
The decision leaves any chance of reducing the routine use of filibusters to block Senate action entirely within the hands of the Senate itself. There, Democratic leaders have been talking about a possible effort at the opening of the next Congress in January to make at least some changes in Rule XXII.
Under Rule XXII, it takes the votes of sixty senators to move ahead with debate or to close down debate on bills or presidential nominations. While the Senate is in the midst of one of its regular two-year sessions, the rule also requires a two-thirds vote to start or close debate on any proposal to change the Senate’s rules. Only at the opening of a new Congress could the Senate change its rules by a simple majority vote.
Judge Sullivan commented that, in today’s Senate, “even the mere threat of a filibuster is powerful enough to completely forestall legislative action.” But, he said, he “cannot find that any of [those who sued] have standing to sue….Second, and no less important, the Court is firmly convinced that to intrude into this area would offend the separation of powers on which the Constitution rests.”
The Constitution, the judge wrote, does not contain any “express requirements regarding the proper length of, or method for, the Senate to debate proposed legislation. Article I reserves to each house the power to determine the rules of its proceedings. And absent a rule’s violation of an express constraint in the Constitution or an individual’s fundamental rights, the internal proceedings of the Legislative Branch are beyond the jurisdiction of this Court.”
