This is perfectly legal, so long as the bowler informs the umpire before changing from bowling left-handed to right-handed or vice versa. Quoting Law 21.1.1, Mode of delivery:
The umpire shall ascertain whether the bowler intends to bowl right handed or left handed, over or round the wicket, and shall so inform the striker.
It is unfair if the bowler fails to notify the umpire of a change in his/her mode of delivery. In this case the umpire shall call and signal No ball.
There is nothing in any of the ICC Playing Conditions for Test Matches, One Day Internationals or T20 Internationals which overrides this.