"It's Real Simple. Putin Is a Kleptocrat"

"He's stealing a lot of money from his country. The money that he's stealing from his country has to go somewhere. So he puts this money into the hands of Russian oligarchs who become his trustees, and they hold this money offshore. In order to steal this money, he's got to commit grave crimes. Sometimes he has to kill people, like he killed my lawyer, Sergei Magnitsky.
"What the Magnitsky Act does is it says that people who commit human rights abuses in Russia and elsewhere can have their assets frozen in the United States and have their visas canceled and have their assets frozen under something called the U.S. Treasury sanctions or the OFAC sanctions list. Why Putin cares about this so much is that it puts his entire business model as kleptocracy at risk. If he's committed crimes, which we can prove that he has, crimes like the murder of Sergei Magnitsky and others, and he has assets overseas, which we can identify, then those assets will be frozen.
"So he feels like all the hard work that he’s done over the last 18 years—all the stealing that he's done, all the people he's had to take hostage and torture and kill—all that hard work is going to be for nothing if that money gets frozen."

At Slate, Jacob Weisberg interviews Bill Browder.

And Adam Davidson at The New Yorker adds an explanation of Russian sistema.