I’d be wary of making it illegal.
I think free birthing is an insanely risky thing to do.
But I know women who’ve had accidental home births because labour progressed much faster than they’d expected. I also know a couple of women - teenagers at the time they were pregnant - who were so deeply in denial about their pregnancies that they’d kept them completely secret until the baby arrived.
So I’d be concerned about the risk of criminalising women who didn’t intend to have a free birth, or where there’s other circumstances that have meant they’re too scared to admit they’re pregnant even to themselves.
I think it’d be much better to look at why these vocal free birthers are rejecting maternity care and to try and address those reasons. And to improve maternity services generally. One of my local maternity units was all over the local news a few months ago because it had been rated inadequate to the point where it was endangering mothers and babies.