This is probably more a question for the family law attorneys; so you may want to post there. Criminally, there is nothing DCF can do. Is this part of a Shelter case? If so, your girlfriend may face the loss of her child if she continues to reside with you and the Court considers you a threat to the child and you are not complying with its orders (the most severe sanction possible). Were you ordered by the Court to do these tests, or is DCF just asking you to do them?
BTW... first question I have seen from Bonifay. My Mom's family is from there and I still have a bunch of family in the area. I need to get up there again and visit one of these days!
I agrree with Atorney Brown, Hopefully DCF won't push the issue further, but technically they could seek to remove the child from your home. Stay clean and be prerared to show a judge you are drug free and that should diffuse the situation if it occurs.
DCF can't do anything to you but they might try to remove the child from the home and place it with an alternative guardian b/c of the drug use. Why did DCF get involved with you and your girlfriend? That's a big element to this DCF issue. If you want DCF to leave you alone, then you need to comply with their plan. As for criminal charges, they can't do anything, but certainly the police would arrest you if you're found in possession of marijuana and/or paraphernalia and that would have an effect on what DCF wants to do.