Sen. Charles Grassley doubled down on questions about Huma Abedin’s unusual employment arrangement in the wake of newly-unearthed emails that illustrate potential conflicts of interest between her three employers.

“How can the taxpayer know who exactly [special government employees] are were working for at any given moment?” the Iowa Republican wrote in a letter to Secretary of State John Kerry Wednesday, referring to the designation that allowed Abedin to work simultaneously for the State Department, the Clinton Foundation and a controversial consulting firm called Teneo Strategies.