Here's a tidbit from NY's ERPO application:
Return guns to respondent. When a final ERPO expires and it is not renewed, the respondent can apply to have any guns that were surrendered to or removed by the police returned.
To make an application to have your guns returned, complete and print the fillable online application form and file it with the court. You must attach proof of ownership and show that you can legally possess the guns. The court will send a copy of the application to the petitioner and any licensing officers who have issued a gun permit to you. If the petitioner or a licensing officer objects to you getting the guns back, the court must schedule and hold a hearing. The court notifies you, the petitioner and the licensing officers of the hearing date. At the hearing, the parties can testify, call witnesses and give evidence to support their side of the story. Then, the court will decide if the guns should be returned to you.
I have no proof that I own any of my guns. I have no bill of sale or receipts and Idaho doesn't require them to be registered. There's no paper trail. If this law was in effect here in Idaho, I wouldn't be able to get my guns back. Then, if whoever filed the application doesn't want you to get them back, regardless of legal ownership, he can drag you through a hearing process.
