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A Colorado man loses custody of his children after getting a medical marijuana card. The daughter of a Michigan couple growing legal medicinal pot is taken by child-protection authorities after an ex-husband says their plants endangered kids.

And police officers in New Jersey visit a home after a 9-year-old mentions his mother's hemp advocacy at school.

While the cases were eventually decided in favor of the parents, the incidents underscore a growing dilemma: While a pot plant in the basement may not bring criminal charges in many states, the same plant can become a piece of evidence in child custody or abuse cases.

"The legal standard is always the best interest of the children, and you can imagine how subjective that can get," said Jess Cochrane, who helped found Boston-based Family Law & Cannabis Alliance after finding child-abuse laws have been slow to catch up with pot policy.

No data exist to show how often pot use comes up in custody disputes, or how often child-welfare workers intervene in homes where marijuana is used.

But in dozens of interviews with lawyers and officials who work in this area, along with activists who counsel parents on marijuana and child endangerment, the consensus is clear: Pot's growing acceptance is complicating the task of determining when kids are in danger.

A failed proposal in the Colorado Legislature this year showed the dilemma.

Colorado considers adult marijuana use legal, but pot is still treated like heroin and other Schedule I substances as they are under federal law. As a result, when it comes to defining a drug-endangered child, pot can't legally be in a home where children reside.

Two Democratic lawmakers tried to update the law by saying that marijuana must also be shown to be a harm or risk to children to constitute abuse.

But the effort led to angry opposition from both sides — pot-using parents who feared the law could still be used to take their children, and marijuana-legalization opponents who argued that pot remains illegal under federal law and that its very presence in a home threatens kids.

After hours of emotional testimony, lawmakers abandoned the effort as too complicated. Among the teary-eyed moms at the hearing was Moriah Barnhart, who moved to the Denver area from Tampa, Florida, in search of a cannabis-based treatment for a daughter with brain cancer.

"We moved here across the country so we wouldn't be criminals. But all it takes is one neighbor not approving of what we're doing, one police officer who doesn't understand, and the law says I'm a child abuser," Barnhart said.

Supporters vow to try again to give law enforcement some definitions about when the presence of drugs could harm children, even if the kids don't use it.

"There are people who are very reckless with what they're doing, leaving marijuana brownies on the coffee table or doing hash oil extraction that might blow the place up. Too often with law enforcement, they're just looking at the legality of the behavior and not how it is affecting the children," said Jim Gerhardt of the Colorado Drug Investigators Association, which supported the bill.

Colorado courts are wading into the question of when adult pot use endangers kids. The state Court of Appeals in 2010 sided with a marijuana-using dad who lost visitation rights though he never used the drug around his daughter.

The court reversed a county court's decision that the father couldn't have unsupervised visitation until passing a drug test, saying that a parent's marijuana use when away from his or her children doesn't suggest any risk of child harm.

But child-endangerment standards remain murky in Colorado, with wide disparities in how local child-protection officers and law enforcement approach pot, said Rob Corry, a Denver lawyer who successfully argued the father's custody appeal.

Corry, who helped Colorado's 2012 campaign to legalize recreational marijuana, said the main thrust of the effort was to treat pot like alcohol.

"Think of brewing beer. You've got a constitutional right to do it. There's nothing wrong with it. Marijuana should be just as simple — you just keep it on a high shelf, right next to your vodka. But in practice, this is not how law enforcement treats marijuana," he said.

In the absence of legal guidelines, a growing network of blogs counsel parents in how to deal with police or child-protection agencies concerned about parental marijuana use, including one, Ladybud, run by legal-pot activist Diane Fornbacher.

She said she moved to Colorado this year after child-protection workers visited her family in New Jersey after a teacher alerted officials when her son mentioned hemp — pot's non-hallucinogenic cousin — at school.

"They said, 'We're just here to help.' Emotionally, my brain was like, 'My kids! My kids!' My mama bear instinct kicked in," she said.

The need for better standards about when marijuana endangers kids is growing by the day, said Maria Green, a Lansing, Michigan, mother who lost custody of her infant daughter for three months last year.

Green grows pot to treat her husband's epilepsy, and though Michigan's medical marijuana law states parents shall not be denied custody or visitation with a child for following the statute, a legal dispute with her ex-husband led to her daughter being placed with a grandparent until it was resolved.

The ex-husband who brought the complaint declined an interview until talking with his lawyer.

"I never in a million years thought that they were going to take my daughter," Green said. "I know that there's a place for child protection, but I would love to see it used to protect kids from being actually hurt."