> but it's like the King's power to veto UK legislation

Honestly this old chestnut comes up time and time again.

As much as many people would love the King/Queen to put the politicians in their place sadly there are two problems.

First, the monarch's role is effectively only ceremonial these days. Even "The King's speech" during opening of parliament is actually a piece of paper written by the ruling-party of the day, the King just sits there in his fancy regalia and reads it verbatim.

Second, if you are referring to veto during the royal ascent process. As per Wikipedia, the King does not have pure veto power, his options are:

    - grant royal assent, thereby making the bill an act of Parliament.
    - delay the bill's assent through the use of reserve powers, thereby invoking a veto.
    - refuse royal assent on the advice of his or her ministers.

None of the above is a pure veto option. The nearest the King can get is delaying it.