I think this is best explained with an example.
To better understand the positions, the royal houses and the states constitute two different spheres, with its own rules and laws.
Example,
Spain 1975: By a law of 1969 that says: that if the Head of State, Franciso Franco, dies, the new Head of State will be Prince Juan Carlos with the title of King. In 1975, Franco has died, Juan Carlos is proclaimed King by state law, but not by the rules of the royal house of Spain.This proclamation violates the rules of the Spanish Royal House that established that Don Juan was the Crown Prince with the right to be King in the event of restoring the monarchy in Spain.
The Spanish royal house in 1975, its Head was Don Juan, it was not Juan Carlos. Don Juan, father of Juan Carlos should have been the King. After the proclamation of Juan Carlos as head of Spanish state, with the title of king by law, his title was created by state law, Don Juan his father, he is still the Head of the Spanish royal house.
Consequences of this:
Hypothesis: if King Juan Carlos had visited Great Britain in 1976, for example, Queen Elizabeth II would have received him with the protocol of a head of state, but would not have applied the protocol to receive a king. An example, Crown Prince Carlos would not have had to bow his head to greet the Spanish head of State, Juan Carlos, even if he had a title created by a 1969 law.
Why? Because in the field of European royal houses, which is where this protocol is applied, Juan Carlos is only the head of state, his title of king is not linked to any royal house. He would be received with the same protocol as a president of the republic.
Another example:
If Queen Elizabeth had held a celebration where all the European royal houses had gathered, as it was in 2012, in the photo who would be sitting as Head of the Spanish royal house, he would be Don Juan. Juan Carlos would not be invited, it is a party of royal houses, not of kings by law.
In 1977, Don Juan, head of the Spanish royal house, in a public act, to correct the situation provoked by law, handed over to his son the rights of the royal house that he represented. Since that day, the title of King of Juan Carlos ceased to be a title created by a law, it was the title of a Royal House. The rest of the royal houses and states with monarchy would apply with him the protocol of the Royal Houses.
Hypothesis, if King Juan Carlos had made an official visit to Great Britain, in 1978,Queen Elizabeth II would apply the protocol of the Royal Houses, she would have gone to the airport to receive the King, and her son Prince Charles, would have bowed his head to greet him .
The same is true in the republics. European royal houses are not recognized, nor are its protocols. The Republic respects what the law of that country says, but does not recognize the protocols of the Royal Houses.
A state with monarchy recognizes the Royal houses and its protocols(Royal houses without a throne are also recognized)A Republic only recognizes the Kings like Head of states, the republic does not recognize the protocols of Royal houses. The Presidents of the Republic and the Kings are received with the same treatment, regardless of the title they carry .In the republics,by example, King Juan Carlos was received with same protocol that a President of Republic,he was King ,because the spanish law said it,but the republics did not recognize him like King of Royal House.
Royal houses have its own normative sphere. When a state changes the law of succession to allow the woman to be Head of State, with title of Queen , for this to have effect within the royal house, it must be accepted by the Head of the Royal House, if this is not accepted, then it would be the same thing that happened in Spain from 1975 to 1977, King juan carlos King of spain by a title created by law that is not a title of a Royal house, because don Juan was Head of royal house that had the right to this title of king.
Regarding Delphine, she is the daughter of King Albert, a judge has said that Belgian law grants her the title of Princess. She is a title created by Belgian law, it is a new title created by the legislator, but no by a royal house, to the rest of royal houses, she is not princess, she is sphere of the law no in the sphere of the royal houses and its protocols. If King Philip says that Delphine is member of the royal house and recognize to her like princess, then she will be princess to the rest of royalhouses and this protocol will be applied for her.
I hope that was understood.
A sphere is the law and other the norms of royal house.
The royal house of greece is recognize by other monarchies and international organist like IOC, he can be named HM KIng constantine.
the royal house of Greece exists has not been exterminated by law,the law has not competence for it. When you refer to the website, first you must say that it is the website of a royal house, he is King, it is his royal house, this Royal house is recognized by all royal houses, and monarchies . And monarchists of the world including Greeks.