President Barack Obama could act without congressional approval to limit a key incentive for U.S. corporations to move their tax domiciles abroad in so-called “inversion” deals, a former senior U.S. Treasury Department official said on Monday. By invoking a 1969 tax law, Obama could bypass congressional gridlock and restrict foreign tax-domiciled U.S companies from using inter-company loans and interest deductions to cut their U.S. tax bills, said Stephen Shay, former deputy assistant Treasury secretary for international tax affairs in the Obama administration.