I think you misunderstood exactly what document Brennan took his oath on - it was a copy of the Constitution before it included the Bill of Rights.. And I must say that this is the trend that had begun before he took his oath... meaning, that the Obama administration seems to care less about our rights as protected under today's Constitution
To me it signifies Brennan's first & foremost a Freemason working for the Illuminati, of which George Washington was an original member of.