Russian policy makers' latest bid to shore up the nation's currency sounds complex but is actually simple: They will take rubles out of the hands of banks.

Fewer rubles means bankers will have less cash to buy dollars. That in turn will stem the selloff in the ruble. Or so goes the argument. On day one, the plan—or at least the unveiling of the plan—worked. The ruble surged 1.7 percent yesterday, to 45.8525 per dollar, rebounding from a record low even as policy makers simultaneously took other steps to allow it to trade freely.

The risk is that the strategy could deepen the economy's slump. Just as bankers will have fewer rubles to buy dollars, they will also have fewer rubles to lend to companies and consumers, choking off credit in an economy already on the verge of recession amid the strain of international sanctions tied to the Ukraine conflict. The Bank of Russia is offering the least seven-day loans known as repos in a month at an auction today.