NICE BUT WHY NOT MAKE THIS RETROACTIVE?

Sec. of the Treasury Jack Lew announced some crackdowns on inversions:

Along with the IRS, the Treasury issued a formal notice that the government said would prevent U.S. companies from accessing a foreign subsidiary's earnings while deferring U.S. taxes through what it called "hopscotch" loans. 

The notice would also prevent inverted companies from restructuring a foreign subsidiary in order to access the subsidiary's earnings tax-free, the Treasury said. 

The move would also block inverted companies from transferring cash or property from what's known as a "controlled foreign corporation" to the new parent company to completely avoid U.S. tax.

And finally, the Treasury said the notice would make it "more difficult" for U.S. entities to invert by strengthening the requirement that the former owners of the U.S. entity own less than 80 percent of the new combined entity.

Unfortunately, currently existing inversions are NOT affected:

The measures, a senior Treasury official said, will take effect for any deal that is not closed by Monday.