A "referee" by any other name.
Sure you can always sue someone - but you will probably find it a lot more cost effective to have a reputable and fair third party to hear the facts of the case and to settle the inevitable disputes that happen when expectations aren't met or scope creep becomes an issue.
And if you don't like the conclusion THEN you can sue them. (But don't be surprised if the court gives you the same result for a lot more money.)