Global tax overhaul faces an unusual hurdle in US Senate debate

An arcane legal argument could America's participation in a global tax deal, backed by 136 countries, in jeopardy.

US president Joe Biden

As the administration of US president Joe Biden and governments around the world celebrate another advance toward an historic global tax accord, an obscure legal question in the US threatens to tear it apart.

At a congressional committee hearing last month, Republican senator Pat Toomey, who opposes the agreement, told Treasury Secretary Janet Yellen that a key portion of the tax deal would require a formal treaty approved by a super-majority in the Senate.