Nancy Schiffer, the White House’s nominee to the National Labor Relations Board, told a Senate panel Tuesday morning that the board lacked the authority to enact any type of union election “card check” rules on its own.

“The provisions of the Employee Free Choice Act require congressional action,” she told Sen. Tom Harkin, D-Iowa, during a hearing before the Senate Health Education Labor and Pensions Committee. The Employee Free Choice Act was the name of legislation Harkin introduced to allow card check elections.

Harkin’s bill, which was strongly backed by unions, would have radically simplified workplace organizing elections by replacing the current system, which usually involves an NLRB-monitored secret ballot election, with what would amount to a petition drive.

When unions try to organize workplaces, they first gather the signatures of a majority of employees claiming they want to be involved in a union. Management can either accept this and negotiate a contract with the union or call in the NLRB to hold an election if it suspects the union got the signatures through fraud or coercion. The NLRB election ensures that a majority of the workers actually want to join.

Big Labor would prefer the process ended when they present the signatures to management. They pushed congressional Democrats hard to change the law after President Obama, who backs card check, was first elected. That effort fizzled out though when moderate Democrats refused to join in.

Nevertheless, several conservative and pro-business groups have warned that the NLRB could enact card check or something similar on its own through labor rules changes. This was part of the reason why Senate Republicans resisted allowing votes on the White House’s NLRB  nominees until last week’s filibuster showdown deal.

Harkin’s question to Schiffer was meant to refute these claims.