Cath, I'm sorry if my post upset you (genuinely sorry) and you're right, I don't have any experience of the family court system, thankfully.
Why didn't your ex request the Judge punish his ex if she was still withholding contact and that was the only option left? I'd gladly punish someone who prevented a relationship between me and my child. I get it would be upsetting to the child, which is something no parent wants but it would be a short-term upset, surely? Once your DH built up a relationship with them, they'd learn themselves he was a good man.
Although I acknowledge alienation does happen, what I don't understand is how? If the parent being alienated always had a good relationship with the children how is it the other parent can damage this with only words? Does it only happen with very young children?
My ex accuses me of alienating his children, whilst actively trying to turn them against me (even though in truth he doesn't actually want them. I have repeatedly offered shared custody up until recently when DD told me she hates going to his house). All he's managed to do is be disowned by his eldest child and frequently in the bad books of the younger one for calling me names and telling lies about me.
I beg both kids to see him because I know the shit I'll have to put up with from him if they refuse. I even invite him to the house to see the oldest, who then promptly barricades herself in her bedroom.
The youngest is also becoming increasingly intolerant of his controlling behaviour and his attitude towards me and refusing to see him more frequently than ever.
I can't stop this, only he can by behaving like a balanced, loving parent. Though, I suppose Ex-H might have more luck alienating the children from me if he at least pretended to be a decent human being.