Don't you read the news in Spanish? That story has been out for many days now.
Additionally, as usual for stories published in English, it has details missing and incorrect.
- The rule isn't new. It is a rule that had been in effect before, but had been suspended in 2006 when the gov't feared that the peso might be getting stronger than desired (how times have changed)
- The banks must divest themselves of dollar cash reserves by the end of the month, but have up to four months to sell off dollar denominated bonds
- There were estimates in at least one article of how many dollars need to be sold (I think it was in the order of $4,000 million)
- New dollar income from external sources (bank lines of credit, money from foreign bank holding companies, etc.) are not subject to the 30% limit
Anyway, this is what is pushing down the dollar right now, and possibly for the next few months, as the banks are flooding the market with dollars, and the selling of the soy harvest begins in March.