Legal Question in Credit and Debt Law in Pennsylvania

You do not post enough details. Has the husband established an irrevocable trust? The answer is yes, its perfectly legal.

However, how is this trust being funded? What does the trust provide for? Why is it irrevocable? Is there some tax reason for doing this?

If the trust is being funded with husband's separate assets, that is his right. If he is funding with marital assets, then the wife would know about it because she and the husband would have to jointly convey the assets to the trust.