Russia's controversial ban on adoptions of Russian children by American families came into force on Tuesday, days after its signing by President Vladimir Putin sparked an international outcry.
The ban is part of a law rushed through parliament to hit back at the United States over its passing of a law sanctioning Russian officials implicated in the death in jail of lawyer Sergei Magnitsky in 2009.
But opponents say it makes Russian orphans -- many with physical or mental difficulties -- the blameless victims of a diplomatic standoff between Washington and Moscow.
The law came into force as expected after being signed by Putin on December 28, Russian state media said.
The blanket ban brings to an end a process that according to the US State Department has seen US families adopt more than 60,000 Russian children over the past 20 years.
It also forbids US citizens who are deemed to have hurt the rights of Russians from entering Russia, and allows the authorities to shut down NGOs funded by the United States.
The ban on adoptions caused an unusual amount of dissent within the political establishment, with Foreign Minister Sergei Lavrov indicating his discomfort and Deputy Prime Minister in charge of social policy Olga Golodets vehemently opposed.
The anti-Putin opposition is trying to play on the splits within the elite by holding a mass rally against the law on January 13 in central Moscow, which organisers hope will muster up to 20,000 people.
The idea of a march through central Moscow ending at the State Duma, which passed the law, has not found favour with the city hall and tough negotiations on agreeing a route are expected after the New Year holidays.
"We will insist on our route," said one of the march's organisers, the journalist and activist Alexander Ryklin.
"I hope that the city hall understands that they need to observe the laws and sometimes remember that Russia has a constitution which is in effect and sometimes needs to be observed," he told Moscow Echo radio.
Activists have said that American families were in particular prepared to adopt ill Russian children and the law risks consigning the most disadvantaged to orphanages for the rest of their childhood.
There is also concern about over 50 children caught in limbo after the law thwarted ongoing adoption processes, where in some cases the orphans had already met future adoptive parents.
Kremlin children's rights envoy Pavel Astakhov has promised they will be found Russian families who will be specially selected by regional governors.
Astakhov has also raised the prospect of the Kremlin banning all foreign adoption in the future, leaving some to conclude the aim is to show Putin's Russia as a strong nation in no need of foreign help.
The US State Department described the ban on adoption of Russian children by Americans as "politically motivated" and said that Washington deeply regretted the move.
Veteran Republican Senator John McCain went even further, saying: "I often wonder how much lower the Russian government under President Putin can stoop.
"But to punish innocent babies and children over a political disagreement between our governments is a new low, even for Putin's Russia."
The death of Magnitsky -- who was charged with the very tax scam that he claimed to have uncovered -- in pre-trial detention in 2009 has become a symbol of human rights abuses in the Russian prison system.
The Russian legislation responding to the US Magnitsky Act was dubbed as the Dima Yakovlev law, named for a Russian boy adopted in the United States who died after being locked in a hot car by his adoptive US father in 2008.