If there's a way you can hold him to the fire on the issue, ITA that it should be done. I have a similar situation. My girls are 4 & 5, very tiny, still harnessed in Maestros in my vehicle. Bio dad has been letting them ride without a car seat since they were infants. No joke. His mother has been written tickets for not having them properly restrained in their car. They only see them a few times a year (holidays) but it's usually for 1 week at a time and he has them for a full 6 weeks during the summer. When they got back from their summer visitation this year, they told me that bio dad allowed them so it in the front seat with just a seatbelt. I want to vomit just thinking about it. We have no clause talking about car seats but we're in the process of going back to court and that will most definitely be brought up. Since we're so far away, the only way I can make sure it's enforced is by hiring a PI. :/ I sent bio dad a text message with the Texas state laws and asked him what he would do if they were in an accident and were seriously injured or killed. He was totally defensive and just had a negative response (we don't get along, ever). I provide him with car seats and up to date safety information so he has NO excuses. It's so stressful and I'm so sorry that you have to deal with the issue, too. I'm planning on booster training my girls and buying some HBB for them so that when they're with bio dad, they at least have those. GL mama, sending lots of prayers and good thoughts your way! Maybe you can request that he be made to provide some sort of letter (or something..?) from a CPST stating that he had the seats inspected? It's what I'm going to *attempt* to do when we go to court.