Legislatures in more than 20 states this year considered laws promoting shared child custody. As the trend toward co-parenting moves forward, lawmakers are pushing to make the arrangement a legal presumption even if parents disagree.

In 2017, Kentucky passed a law that made equal parenting time and joint physical custody standard for temporary orders during the finalization of a divorce. Florida also passed legislation that presumed equal time for child custody agreements, although the governor ultimately vetoed the bill. Michigan is mulling over a bill that would make equal parenting time the starting point for divorcing parents.

The push for equal parenting time comes after years of lobbying from fathers’ rights groups, who argue that men feel alienated from their children and overburdened with child support obligations.

In shared custody arrangements, children spend at least two overnights with each parent every week, or the child spends every other week with each parent.

While the measures have gained broad support on the political spectrum and among Americans, some argue that co-parenting can put some children in danger.

Critics say stricter laws will remove protections against controlling and abusive parents. Others claim the measures remove judge discretion when deciding what’s in the best interest of a child.

Co-parenting laws may eventually eliminate child support in some states, women’s rights groups argue.

Court decisions regarding child custody have been guided by the “tender years doctrine” for more than a century. The “doctrine” paints women as instinctive caregivers.

That sentiment began to shift in the 1960s and 1970s when more women entered the workforce and no-fault divorces became the norm. But to this day, judges continue to use discretion and award primary custody overwhelmingly to women.

Maryland, the District of Columbia and Virginia have either passed or are considering legislation that presumes co-parenting is in the best interest of the child, except for in cases of abuse and neglect.

Changes in child custody arrangements has been fueled by both fathers’ rights groups and science. Social-science research shows that children benefit from having equal time with both parents. When children have active fathers, they tend to do better in school and have higher levels of self-confidence.

But some question the validity or research related to children in co-parenting situations. Critics argue that children in joint custody arrangements generally have parents that get along better than those in conventional custody arrangements.

To tackle this issue, many states are promoting the use of parenting plans and mediation instead of battling child custody matters in court. Custody plans detail each parent’s responsibility for the child’s care. Data shows that this route typically leads to more equitable parenting time.

Still, a number of stay-at-home and younger dads are frustrated with the slow progress of shared custody arrangements, and are pushing for changes in the family court system.

Those opposed to sweeping custody law changes say quality trumps quantity when it comes to parenting time. Law changes may leave some children in the middle of a constant war zone, which may damage their relationships with their parents.