In Oklahoma, it is legal to record a conversation as long as one person is aware the conversation is being recorded. Get a recorder and record this stuff as it will go a long way if he files to modify custody. Your niece is only required to follow the court order but if they have agreed on differerent terms, I would document where he isn't following that. Also, get a diary and record everything...times dates and incidents. If he brought child back late, record it in diary.
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