I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
Initially, the parents may want to call police again, tell them they have a birth certificate, and that their child has been kidnapped by a non-parent. Talk to a superior officer if necessary. it's a civil dispute when either father or mother withholds the child from the other because both have equal custody in the absence of a court order. But a grandparent has no automatic right to custody the way a parent does. They could also say "I'm going to pick up my child from the grandparent's house, and I need you to do a civil standby to ensure that there isn't any altercation." (That's something police do fairly regularly.)
The other option is to go to the courthouse at the moment it enters and file an Emergency Petition for Sole Custody. Explain to the judge that the grandparent has taken the child without authorization or excuse and that for reasons beyond comprehension, police will not assist in getting the child back. It would help if both parents signed the petition, but it can be done by either alone. Usually, when someone files an emergency petition, they go before the judge right away. So she could get an order in a few hours. The process may be less stressful if a local attorney helps, but it can be done by either parent.
The Petition for Custody form is here. This is a regular, non-emergency form that establishes a case and tells the judge that there's a custody issue. An emergency request is a separate document that explains why this is an emergency and why the parents need to get a court order ASAP. The courts don't generally make emergency petitions available, so it's something you'd write yourself. But the fact that the PA has no legal basis whatsoever for withholding the child should help considerably.
If police help with retrieving the child, then an emergency petition is not necessary, but filing the regular petition for custody and support may help avoid this issue down the road.
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