I was going to say something very similar charlyfrog
I believe if he is capable of opening drawers/boxes etc and pulling everything out and making the mess then he is able to put it back - with guidance.
I am thinking that this is more a boundary pushing issue more than anything as it is only in the last couple of weeks we have had problems and also he has been playing with the same toys over & over so boredom is probably kicking in a bit.
I have removed the *offending* toys and yesterday he played with toys from his room that haven't seen the light of day for ages and np with tidying up.
But a huge thank you to everyone for their input it has all been appreciated.