The US had a law (the Jackson-Vanik Amendment) banning trade with all countries that did not allow their citizens to leave. It was intended to target communist states like the Soviet Union.
Russia just joined the World Trade Organization in August (largely due to the support of the US), so Congress had to repeal the the Jackson-Vanik Amendment and replace it with a law establishing normal trade relations with Russia. Some members felt that the new law should be conditional on respect for human rights, so they included provisions that would deny visas to any foreign persons accused of human rights abuses, and freezing their assets in the US (i.e., bank accounts), if any. To drive the point home, they named the bill the Sergei Magnitsky Act, after a Russian lawyer who was tortured to death in a Russian prison after accusing Putin's government of corruption.
International human rights and humanitarian law is a particular interest of mine, so I have no problem with the law. Putin's regime has been responsible for the murder of an incredible number of courageous journalists, lawyers and other dissidents, and I don't believe that countries that deny basic freedoms should be rewarded.
Some of you may be familiar with Anna Politkovskaya, who was gunned down in briad daylight after reporting on the brutal war in Chechnya, or Aleksandr Litvinenko, a former KGB agent who died from radiation poisoning in London after openly criticizing Putin's government. Two foreign policy experts died under mysterious circumstances within days after appearing in a Dateline NBC segment about Litvinenko's murder. Journalist Ivan Safronov "fell" from his apartment window to his death. And on and on and on ...
Unfortunately, I think the United States has committed so many human rights violations over the past decade that we no longer have the high moral ground. The only difference is that Putin's crimes are against his own people, whereas ours are outside of our borders. So I'm personally torn over this issue. And the worst thing is that the children suffer the consequences of a geopolitical game.