The top Republican on the banking committee has written to President Joe Biden questioning the geographic and industrial diversity of his Federal Reserve picks, raising the specter of legal problems that could threaten the nominations.

Sen. Pat Toomey raised the problems about the people Biden recently nominated for crucial positions at the central bank in a Tuesday letter to the White House. The Pennsylvania Republican hinted that Biden’s picks could be in violation of the Federal Reserve Act and said he is seeking clarification on the matter.