Does ethics support the law in this case?

Actually, this scenario, though similar stories have actually happened, supports neither. Both ethically and legally, the family court is obligated to rule "in the best interests of the minor."

No reasonable person should think removing a nine year old child from the only family she's ever known and forcing her to live with strangers is in her best interest.

That's why cases like that make the media. They are the exception, not the norm. They are egregious, so they make for sensational headlines and footage. Wrong on so many levels. :/

I found this which may interest you.

The National Conference of Commissioners on Uniform State Laws approved in 1994 a model adoption statute, which was designed to reduce the chances that custody will be changed after children have become attached to parent figures. The model statute provides guidelines for birth parents and adoptive parents to follow before an adoption in order to prevent custody battles afterward.

In the 1990s, courts appeared to place more importance on child-caretaker attachment and in some cases even denied custody to birth parents in order to uphold this attachment. A Florida judge ruled in 1993 that 14-year-old Kimberly Mays could choose not to see her birth parents, from whom she had been separated at birth by a hospital error (Twigg v. Mays, 1993 WL 330624 [Fla. Cir. Ct.]). The decision was based on the length of time she had spent with her nonbiological family and her attachment to it.

Ethically the parents are in the right, as well as legally. This is more a question of Law versus Justice. If you have read any of my other answers you will have heard me say that the law and justice are two entirely different animals. In the scenario that you posed for us, the law is satisfied but by no stretch of the imagination can you call the outcome justice for the little girl or the Foster parents.

The parents as you said was rehabilitated from the use of drugs and therefore can stand fit and ready to take their responsibility to take custody of their child which is now 9 years old. No law or country should deprived a mother or a father or the parents to take good care of their child. Are you a father or a mother? Not yet I suppose so you do not know the real agony and feeling of loosing a child.

So the court grant the custody of the child to the real parents, it is time that the child should now adjust to his or her new environment and learn to love his or her real parents. We all make mistakes in this life time. Whether we are rich or poor, temptation is all around us.