Today, Senate Finance Committee Chairman Orrin Hatch (R-UT), Ranking Member Ron Wyden (D-OR), Senator Rob Portman (R-OH), and Senator Charles Schumer (D-NY) sent a letter to Treasury Secretary Lew regarding the European Commission’s state aid investigations of tax rulings given by member states to US companies or their subsidiaries. The letter expresses concern that the rulings could lead to retroactive taxation on multinational enterprises. The letter also says that the European Commission “appears to be asserting supremacy over and becoming the final arbiter of transfer pricing and other international tax determinations in the EU.” They also point out that four of the five investigations of company-specific tax rulings involve US companies and that “encroachment on U.S. tax jurisdiction that results from these cases appears to be intentional.”