An inconvenient question: How can a bitcoin be "laundered"?

If a bitcoin can be faked then sure - but I find it odd that a nation that hasn't embraced bitcoins sees fit to enforce the legitimacy of the currency. Or has Greece actually embraced bitcoin as legitimate tender?

Even if bitcoin is legal tender in that nation and even if bitcoins can be faked - I am curious as to how they feel to be competent to determine a real bitcoin from a fake one.

I am merely taking this story with a chunk of salt.