Attorneys for Slaughter, a Democrat, argued she should be reinstated because of a 90-year-old ruling, Humphrey's Executor vs. United States, that said Congress had the authority to limit the president's ability to fire independent agency heads. Humphrey's Executor's reach has been steadily chipped away by decisions over the past two decades and the conservative justices at the court appeared to agree with the administration that prohibiting Trump from firing trade agency commissioners except in cases of "inefficiency, neglect of duty, or malfeasance in office" violates the constitutional separation of powers between the three branches of government. 

The current high court, under Chief Justice John Roberts, has shown a willingness to revisit cases long-held as precedents — such as Chevron vs. Natural Resources Defense Council and even Roe vs. Wade — when a majority of the justices felt those precedent-setting cases were either wrongly decided or applied improperly by subsequent rulings.

Loper Bright Enterprises vs. Raimondo, the decision that last year overturned the long held Chevron ruling, had wide implications for construction as agency heads no longer held the ability to interpret the law to create policy for four or eight years, deciding the impact of what defines "waters of the United States" or other terms in law. 

The Slaughter decision may impact construction projects even more directly as Trump has already removed members of the National Labor Relations Board as well as Federal Trade Commission appointed by predecessors, although commissions generally are made up of bipartisan members.

In the questioning, Solicitor General John Sauer said independent agencies are a "headless fourth branch" with limited government oversight and that, in general, "are not accountable to the people." He said the 90-year precedent, Humphrey’s Executor, "must be overruled." describing the ruling as a "decaying husk with bold, and particularly dangerous pretensions."

Sauer found unlikely agreement, seemingly, in Roberts who prefaced one of his questions by saying historic precedent has "nothing to do with what the [federal trade commission] looks like today."

Justice Sonia Sotomayor, however, told Sauer that his argument would put independent agencies  "at risk" without the benefit of congressional protection from executive action. “You are asking us to destroy the structure of government,” she said. Justice Elena Kagan added that presidential intervention in independent agency governance is "going to put a lot of the legislating and adjudicatory power in the hands of the president. You end up with massive, unchecked power" controlled by a president.

Justice Amy Coney Barrett countered in her questions that Congress once had a legislative veto over the comissions, which  — until the Supreme Court held it unconstitutional — allowed it to overturn decisions by administrative agencies. She contended that independent agencies are now not accountable to either Congress or the president, claiming that the situation now is "something that Congress didn’t intend."

A high court ruling is expected by next June or early July.