This is all based on the concept that a certain ancestry (a better definition than "race") should lead to special legal entitlements or benefits not available to the general population. This concept  isn't very appealing in the case of an aristocracy, and despite well-meant intentions,  it is fraught with the kind of problems that the author quite accurately points out.  Should having one indigenous ancestor out of 5 or 6 generations give me special constitutional status/rights? Why? If something more is required (community recognition, lifestyle, language, etc.), than determining who falls within the definition becomes very challenging.