A lot of eyebrows were raised when the news came out Wednesday that Pfizer had approached Allergan regarding the possibility of a merger. Allergan is based in Ireland, so there can be no doubt what Pfizer’s real intentions are in showing up on the scene as an uninvited suitor.

Pfizer execs have long seen the handwriting on the wall for regarding the “patent cliff” they face and the closing window for corporate inversions and all the attendant tax benefits, so they apparently decided to try and solve all their problems in one fell swoop. Snapping up rapidly growing Allergan can fix all their problems, and save them a bundle in taxes, so they decided to strike while the iron was hot.

Unfortunately for Pfizer, American patriot and hedge fund billionaire Carl Icahn heard about this nefarious scheme, and has written a letter to the U.S. Congress telling legislators  to pass a new law to stop this corporate inversion nonsense pronto.

Pfizer Car  Icahn
Via S&P CapIQ

Excerpt from Carl Icahn’s letter to Congress

In his letter, Icahn explains his problem with a Pfizer – Allergan merger: “Allergan is domiciled in Ireland, and if consummated, this will be the largest corporate inversion to date, and as a result our country will lose Pfizer, its tenth largest company. The imminent planned exodus of many of our best companies is extremely dangerous, especially in our fragile economy, as it will cause the loss of thousands of jobs, as well as hundreds of billions of dollars of future tax revenue and investment in the United States.”

Icahn goes on to suggest that Congress should add an amendment to the currently-under-consideration Highway Bill to ban these kind of purely profit-motivated and unAmerican corporate inversion deals.

He writes: “The Highway Bill presents an immediately available opportunity to pass international tax reform that will stop inversions. In the conversations I had with many of you, there was universal agreement on this fact as well. But our window of opportunity is shrinking. The most recent short-term extension to the Highway Bill gives us only until November 20th to pass a long-term Highway Bill that includes the international tax reform necessary to stop further inversions. If a version of the Highway Bill passes without including this necessary tax reform, I fear we will lose many more iconic companies, such as Pfizer, in the months to come.”

Allergan has a market cap of around $115 billion. That means that a merger with Pfizer would be valued at well over $300 billion, the biggest takeover so far in a year that is on pace to set records for mergers and acquisitions activity.