Not only do they make their own rules, the DNC has argued in court that they have no obligation to follow those rules since they can change them whenever they want anyway.

“But here, where you have a party that’s saying, We’re gonna, you know, choose our standard bearer, and we’re gonna follow these general rules of the road, which we are voluntarily deciding, we could have — and we could have voluntarily decided that, Look, we’re gonna go into back rooms like they used to and smoke cigars and pick the candidate that way. That’s not the way it was done. But they could have. And that would have also been their right, and it would drag the Court well into party politics, internal party politics to answer those questions.” - DNC attorney Bruce Spiva