Here in Canada I know that once the children have been removed it can take some time and positive actions on the parents part to get them back. The social worker is responsible for the child first and foremost, as it should be. For the parents it is very much a "don't tell me, show me" situation and the more clean time as well as progress in recovery actions will help. In some cases parenting classes are helpful, or anger management or any counseling specific to their situation over and above the addiction. Also, employment and showing that they are capable of providing the needs for the child, financially and emotionally, are important.
I agree with getting a legal opinion, but the best thing may be to just work closely with the social worker and do the "do" things she requires.
My prayers go out that his family can continue to heal and be united in a healthy environment soon.
Hugs