A short while ago, some commentators declared that the Treasury had successfully ended corporate inversions. But after several recent corporate migrations, reports of the inversion’s death appear to have been greatly exaggerated.

A corporate inversion is a complicated and costly transaction used by American corporations to avoid particularly burdensome aspects of the U.S. tax code. The United States not only enforces the OECD’s highest corporate tax rate (the tax rate for most U.S. corporations ranges between 35% to 39%) but also worldwide taxation. This latter feature subjects an American corporation’s entire revenue stream to the United States’ extraordinary tax rate, whereas most countries tax only what is earned inside their territorial borders. In simplified terms, a corporation hoping to invert must merge with a foreign corporation—while satisfying some very idiosyncratic conditions—in order to reorganize in the foreign company’s country. After inverting, a company’s foreign generated income becomes subject to more favorable foreign tax rates, though it must still pay U.S. taxes on domestically generated revenue.

The rhetoric surrounding inversions has been heating up since Pfizer announced its intentions to invert into an Irish entity after acquiring Allegran in a $160 billion deal. The chief complaint against inversions is that inverted companies…