Putin wouldn't put his money into Bitcoin because more than likely his address(s) would be blacklisted by mining pools, which will be enforced by governments.
Nobody can really force this. How would you know which addresses are his? He could mix this up beyond tracking.
Storing money in a bank is less safer than storing it in a wallet file.
I don't however understand what Obama think he will achieve with this? This won't stop Putin, nor does he care at all.