Dai Xiaolei last saw her son in 2014, when he was 17 months old and living with her in-laws in Baoding, a city in Hebei province about 156 kilometers from Beijing.

Her marriage was crumbling and, as relations deteriorated, she claims her husband's family blocked her from taking her son with her back to the capital.

"The last time I saw my son was at the end of this alley. It's like a fortress," the 37-year-old said outside her in-laws former home.

Reuters was unable to independently verify Dai's claim that the family has blocked all attempts to see her son.

Her husband, Liu Jie, filed for divorce, arguing that the marriage had fallen apart due to "conflicts in character, ideas and living habits", according to court documents. Dai pushed for custody, but in April, a judge ruled that it was best for the boy's physical and mental health to stay with his father.

Liu, a movie stunt coordinator, and his parents declined to comment.

As China's divorce rate rises, so too have calls by legal professionals for new laws that would clamp down on aggressive tactics used by some parents to take or retain possession of a child to gain the upper hand in custody battles.

Lawyers say judges tend to favor the parent who already has physical possession of the child in order to avoid further disruption to their life.

Dai appealed the custody ruling and lost. The court said the child's living environment was relatively stable and any change would not benefit his upbringing.

There are no laws against one parent taking sole possession of a child against the wishes of the other, lawyers say, reflecting a traditional view that family conflicts should handled privately.

The Supreme People's Court declined to comment on specific cases, but it said, "Maximizing benefit to the child is the basic principle by which custody decisions are made."

Joint custody rare

China's divorce rate more than tripled between 2002 and 2015, reaching 2.8 per 1,000 people, according to the Ministry of Civil Affairs. This is higher than the most recent estimate for the European Union (2.1 per 1,000 people in 2011) and is not far off the rate in the United States (3.2 in 2014).

While no official data is available publicly, Yan Jun, a district court judge in Beijing, estimated that one parent will snatch a child from the other in 60 percent of cases in which both spouses are seeking custody.

Under the law, parents are rarely granted joint custody, as is the case in some countries. Instead, judges usually give one parent "direct custody", often preferring to maintain the status quo living arrangement for a child aged 2 to 10.

A lawyer at a Beijing family law firm, who declined to be identified, said child-snatching regularly takes place before divorce proceedings, which allows one parent to argue the child has a stable living environment. Li Ying, a Beijing lawyer and advocate for parental rights, said snatching tactics should be prosecuted when a new domestic violence law is enacted in March.

Under this law, beatings, verbal abuse and threatening behavior are considered forms of domestic violence. Some family law experts have said preventing a child from seeing their mother or father, or vice versa, should also be considered psycho-logical abuse.

Even when judges rule in their favor, some mothers complain about a lack of enforcement and sometimes take matters into their own hands.

One, who did not want to be named because her dealings with the courts are still ongoing, said she hired a private detective who found her son living under a fake name with her ex-husband's aunt in northern China.

The court had awarded her custody, but when she complained months later that the order had not been enforced, a court official was blunt.

"She told me: 'Don't just depend on the courts. Are you working hard enough or are you just depending on us to get your child back?'"