Because the oath of office doesn't oblige him to do anything if he recited the Kol Nidre on the Day of Atonement before he took it.
"All vows we are likely to make, all oaths and pledges we are likely to take between this Yom Kippur and the next Yom Kippur, we publicly renounce. Let them all be relinquished and abandoned, null and void, neither firm nor established. Let our vows, pledges and oaths be considered neither vows nor pledges nor oaths."
Keeps the letter but not the spirit of the law? Hmmm where have we heard that before?
Let's hope that Q's hints that he might be starting to cooperate will be proven right. But lawyers, you know…. very wriggly people.