And it must be fairly specific, so can't just be that everyone must be nice to everyone.
Please state, law , purpose, possible complications/details as necessary.
Mine: any person who had sex and became a parent would be financially liable for 50 % of money to raise that person until they were independent.
Purpose: hopefully, people would not have unprotected sex but would think about the outcomes of their actions, and one parent couldn't bugger off and make the other live in penury whilst they dodged the CSA.
Details: DNA tests would be necessary, some parents would need benefits to help them pay, women would have to have private counseling before a termination to prevent coercion. The child would be considered independent at age 18 or when leaving school. I cases of rape, the rapist would be liable for 100% of costs to raise child. Absolutely no link between the duty to pay and any rights to see the child.
What law would you pass?