It should do a long as he and his employer are complying with H&S rules! If you send him up a ladder and he isn't trained or it's not suitable for the work etc then you might be liable!
Does that mean sending him on some kind of 'training' course rather than just showing him yourself?
No need for sending him on a training course, he'd have to have been shown how to safley use them though, and he'd have to have a record saying hes been shown signed by the employee to say that he'd been shown how to use them.
I hope he has records of checks of the ladders to make sure there still safe etc.
Lets be honest, he's phucked, as he's not going to have all of that.