A filibuster is part of parliamentary procedure which most all governmental bodies follow to run their meetings. It allows 1 or more members to delay votes and so yes, it is legal. It was seldom used in Congress up until the 1960's but since then (possibly with our more polarized political system) it has become more frequently used. The filibuster was strengthened in the Senate in 1975.

There are 2 ways to stop a filibuster. One, if the individual or group quits talking, they lose the floor in essence. The more likely way it can end is if 3/5ths of the Senate votes for closure of the filibuster. That requires 60 senators to agree which is unfortunately difficult in today's climate.

A filibuster is not just used in the United States but all over the world. Hope that helps.   

You missed the point of my question. Who has the standed to challenge the legality of the parlimentary rules? Plenty of stuff is legal, until it isn't. I know the supreme court is general loathe to get involved in congressional procedures, but who could bring such a case before the court?

I apologize if I misunderstood the question. Generally, anyone can file a court case to determine the legality of an issue, this one included. I would think a case or situation like this would have to be taken to court from a group such as the ACLU or other that is willing to do it. The main issue is going through any court (local, appellate, Supreme) takes someone who has the money to hire an attorney or law firm to take it as far as they can. This amounts to thousands and hundreds of thousands in Supreme Court cases which is why there are not more than there is. The Supreme Court also determines which cases it will hear.

I'm not trying to be negative, but with the current court system glut as it is I am not sure a case on the legality of a filibuster would receive a very high priority but I could be wrong.