Yes but the last time a monarch vetoed a law was in 1707, and that was only because parliament asked Queen Anne to veto the law.
In reality, if King Charles started vetoing then after a short constitutional crisis, parliament would basically just change the rules of the game to say that the monarch no longer has the power to veto laws.
In reality, if King Charles started vetoing then after a short constitutional crisis, parliament would basically just change the rules of the game to say that the monarch no longer has the power to veto laws.