After the Sonny tragedy and the Don meets with Barzini and the others - he says now he has to clear his youngest son from the Solozzo charges.
Now I have not yet read the book, but I understand that to mean Michael is in a lot of trouble from the law when he gets back to the states - but who knew he did it? I mean besides the other 5 families, but they wouldn't say anything to the law, would they?