What Is Plenary Authority? Meaning Explained as Stephen Miller Sparks Debate Over Presidential Power

Stephen Miller, White House deputy chief of staff for policy, sparked fresh debate in the United States after claiming that the president has 'plenary authority' to deploy military forces under federal law.

The comment, made during a live CNN interview this week, quickly went viral after Miller appeared to pause mid-sentence while defending the scope of presidential power.

The moment drew widespread attention across social media, prompting many viewers to ask what 'plenary authority' actually means and whether any US president truly holds such unrestricted control.

Legal experts, political commentators, and social media users have since weighed in, arguing over whether the term reflects legitimate constitutional power or political overreach. The controversy comes amid renewed scrutiny of executive authority as the Supreme Court prepares to examine several cases involving presidential powers in its new term.

What Is Plenary Authority?

'Plenary authority' or 'plenary power' refers to full and complete authority within a specific area of governance. In legal terms, it suggests an ability to act without needing additional approval.

However, in practice, such authority is almost never absolute in democratic systems. Constitutional and statutory checks usually limit how far this power can be exercised.

In the United States, the phrase has appeared in several key legal contexts. Congress has historically been said to possess plenary power over immigration and nationality laws, meaning that courts have often deferred to legislative decisions in those areas.

Similarly, the Supreme Court's 1892 ruling in McPherson v. Blacker recognised that state legislatures have plenary authority to decide how presidential electors are appointed. Even so, modern courts have maintained that constitutional rights and due process still place limits on these powers.

Stephen Miller's Claim and the Backlash

During the CNN interview, Miller asserted that the president holds plenary authority under Title 10 of the US Code to deploy the National Guard, even if local or state governments oppose such action. He stated that this authority allowed the president to act independently in ensuring national security and public order.

The remark immediately drew criticism from legal analysts, who challenged the claim's accuracy. Many argued that while the president has significant powers under the Insurrection Act and other statutes, those powers are not without oversight.

According to constitutional scholars, no US president has ever held unlimited authority to deploy troops within the country without following statutory procedures.

The incident gained further attention after video clips of Miller's apparent hesitation circulated online. Some commentators suggested that he may have realised the legal implications of the phrase as he spoke. Others said the exchange highlighted ongoing efforts by certain political figures to test the boundaries of executive power.

The Legal Context and Current Relevance

The concept of plenary authority sits at the heart of longstanding debates about the separation of powers in the United States. In 19th-century cases such as Chae Chan Ping v. United States, the Supreme Court treated immigration control as an area where Congress and the executive branch held broad, nearly exclusive authority.

However, modern interpretations have become more constrained, particularly where constitutional rights are at stake.

The current Supreme Court term is expected to revisit questions surrounding executive authority, including the president's power to impose tariffs under the International Emergency Economic Powers Act (IEEPA).

Meanwhile, Congress has introduced the Trade Review Act of 2025, aimed at increasing legislative oversight of presidential trade decisions.