Does it make the farmers' market unfree when it declares a rule that vendors may not purchase their wares (but must grow the produce/animals on a farm)? Does that make the farmers employees of the farmers' market? Without getting into the finer points of law about contractor independence & discretion, it's a bit silly to hold the position that Uber can't regulate the service in any way. In particular, standardizing the terms of the contract to be traded in a given market is a practice even the staunchest of free market proponents accept.