Actually, you make a good point JosephMalik, the word "over" is ambiguous in English. Just like the word "with", which can be used for both instrumental ("I cut the bread with a knife") and accompaniment senses ("I went to the park with John"). The same goes with "over". In English, "over" can indicate a spatial location ("The astronauts were orbiting over Africa when they received the transmission"), as well as a non-spatial relation of power ("The king ruled over his subjects"). Epi is not used to indicate a spatial relation of "over" (its spatial relation is "on" or "upon"), the proper word for that is huper. So if the Society uses the probable genitive of subordination in Revelation 5:10 as indicating a location of the anointed rulers over the earth, i.e. in heaven, then that would be a misinterpretation of the given text (even if the NWT rendering is permissible).
And there we may discover the value of this thread....for indeed this misinterpretation can be found in Watchtower publications:
*** w06 8/15 pp. 6-7 "As in Heaven, Also Upon Earth" ***
This salvation with two destinies, heavenly and earthly, is mentioned in a vision seen by the apostle John. He saw kings on heavenly thrones who had been chosen from among Christ’s faithful disciples. The Bible specifically states regarding these associates of Christ that "they are to rule as kings over the earth." (Revelation 5:9, 10) Note the dual aspect in the accomplishing of God’s purpose -- a restored earth under the direction of a heavenly Kingdom made up of Jesus Christ and his joint heirs.
*** w78 3/1 p. 21 par. 1 “The Kingdom of Our Lord and of His Christ” Takes Over ***
Then they will no longer be earthly subjects of a spiritual kingdom of Christ, but they will be kings with him in heaven. This prospect agrees with the words of Revelation 5:9, 10, addressed to Jesus Christ, the Lamb of God: "With your blood you bought persons for God out of every tribe and tongue and people and nation, and you made them to be a kingdom and priests to our God, and they are to rule as kings over the earth."
The goofy Revelation Climax
book oddly enough does not make this mistake. What is really odd though is a QFR that explains why the NWT is correct for rendering the epi
as a genitive of subordination, bringing a knowledge of Greek grammar to bear, but then it goes right ahead and makes a doctrinal interpretation that ignores the genitive of subordination and takes the epi
incorrectly as spatial:
*** w74 12/1 pp. 735-736 Questions From Readers ***
The basic significance of the Greek word epi is "on" or "upon," but that is not the only meaning. When used in connection with power, authority or dignity, epi can also mean "over."
Numerous Biblical examples illustrate this. God is referred to in the Bible as being "over [epi] all." (Rom. 9:5; Eph. 4:6) The Ethiopian eunuch was "over [epi] all" the treasure of Candace. (Acts 8:27) The "faithful and discreet slave" is appointed by his master "over [epi] his domestics." (Matt. 24:45) Seven certified men were to be selected by the Jerusalem congregation that the apostles might "appoint them over [epi] this necessary business" of food distribution. (Acts 6:3) Clearly, in all these instances the Greek word epi followed by the genitive case cannot be translated "on" or "upon," but, in harmony with the context, is properly rendered "over." —Note also Revelation 9:11; 11:6.
Likewise, at Revelation 5:10, those entrusted with rulership are in charge of the earth, exercising dominion over those dwelling on it. The subject matter of this text is rulership, and logically, therefore, the Greek word epi calls attention, not to the location of the rulers, but to the area over which they exercise authority. That they rule "over the earth" agrees with the rest of the Scriptures, which reveal that God’s kingdom by Christ is heavenly and that Jesus’ associate rulers are promised heavenly life.
Isn't that amazing? They say that "over" does not indicate "the location of the rulers", and yet for doctrinal reasons they still insist (despite their description of the genitive of subordination) that epi is still spatial, and thus indicates "the area over which they exercise authority," allowing them to sneak by with letting that define the spatial location of the rulers "in heaven". Just look at the other examples of epi that they cited -- the sense is properly "that over which one exercises authority" or "those over which one exercises authority", not "the area over which one exercises authority". Usually, when a king rules over his kingdom, he is not himself located outside the kingdom or literally over it. He is in it. That doesn't necessarily mean that the rulers in our present text are in the domain of the earth (although a spatial reading of epi certainly means this -- remember the preposition is ambiguous in this context), it just means that the word "over" is not used spatially in this context if it is to be read as a genitive of subordination.