Trump’s deployment of National Guard troops reignites a 200-year-old constitutional debate

This article originally appeared on The Conversation.

If you’re confused about what the law does and doesn’t allow the president to do with the National Guard, that’s understandable.

When National Guard troops landed in Portland, Oregon, in late September 2025, state lawyers argued that the deployment of the National Guard was a “direct interference with sovereign police authority.”

Read more: The US Court of Appeals says Trump can take command of the Oregon National Guard, although their deployment is currently prohibited

Days ago, President Donald Trump, who described the city as a “war zone,” invoked a federal law that allows the government to call in the Guard during national emergencies or when state authorities are unable to maintain order.

This conflict highlights a question as old as the Constitution itself: Where does federal authority end and state authority begin?

One answer seems to appear in the direct language of the Tenth Amendment: “The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.” This text is considered the constitutional “hook” of federalism in our democracy.

The Founders, in response to Anti-Federalist concerns about an overbearing central government, added this language to emphasize that the new government had only limited powers. Everything else – including broad “police power” to regulate public health, safety, morals, and welfare – remained in the hands of the states.

However, from the beginning, the text generated a lot of confusion. Is the Tenth Amendment merely a “self-evident truth,” as Justice Harlan Fiske Stone wrote in 1941 in United States v. Darby, rewriting the Constitution’s limited-powers structure? Or does it describe the concrete powers possessed by states?

It turns out there is no simple answer, not even from the nation’s highest court. Over the years, the Supreme Court has treated the Tenth Amendment like a magician’s hat, sometimes pulling powerful state powers from deep within, other times finding them empty.

The scope of the Tenth Amendment is broad

Arguments about the Tenth Amendment have applied for nearly 200 years not only to the National Guard, but to questions about how federal and state governments share powers over everything from taxes to government salaries, law enforcement and regulation of the economy.

For most of the nineteenth century, the Tenth Amendment remained dormant. The weakness of the federal government and its limited ambitions, especially regarding the issue of slavery, meant that the limits were rarely tested in court.

The New Deal era led to the collapse of this balance.

The Supreme Court initially resisted the expansion of federal power, striking down laws prohibiting child labor in Hammer v. Dagenhart in 1918, setting the federal minimum wage in 1923 in Adkins v. Children’s Hospital, and offering subsidies to farmers in United States v. Butler in 1937. All of these decisions were based on the Tenth Amendment.

He watches: Conservative constitutional lawyer comments on Trump’s aggressive use of executive power

But this resistance declined in the face of the economic crisis and political pressures. By the time of the Darby case in 1941, which concerned the Fair Labor Standards Act and Congress’s power to regulate many aspects of employment, the Court had relegated the Tenth Amendment to “self-evident” status: Stone wrote that the amendment did nothing more than recast the relationship between the national and state governments as established by the Constitution before the amendment.

The 1970s saw an unexpected revival. In the 1976 decision in National League of Cities v. User, a dispute over whether Congress could directly exercise control over minimum wages and overtime wages for employees of state and local governments, the Court held that Congress could not use its mercantile power to regulate state governments.

But this principle was abandoned nine years later, with the court doubling down on its position. Now, if states want protection from federal overreach, they must seek it through the political process, not judicial intervention.

However, less than a decade later, the court reversed course again. The renaissance of modern federalism began in the 1990s with divided opinions suggesting that the federal government could not force states to enforce federal regulatory programs: this was the “anti-control doctrine.”

The winding path of the Tenth Amendment

In recent decades, the Court, led by Chief Justice John Roberts, has invoked this amendment to protect state power in diverse, even surprising, contexts: states’ entitlement to federal Medicaid spending; State authority to administer elections, despite patterns of voter exclusion; Even legalize sports gambling.

On the other hand, in 2024, the court blocked Colorado from excluding Trump from the presidential ballot as part of its authority to administer the election.

This brings us back to the present, where Trump has deployed National Guard troops to Los Angeles to quell protests against immigration enforcement, and is trying to send them to Portland and Chicago as well.

From a federalist perspective, there are two factors that give this conflict some constitutional complexity.

The first is the dual federal character of the National Guard. Most Guard mobilizations, including disaster relief, are done under Title 32 of the United States Code, which maintains state control over federally funded forces.

By contrast, Title 10 allows the President to assert federal control over Guard units in the event of “rebellion or danger of rebellion” against the government or when “the President is unable with regular forces to execute the laws of the United States.”

The other factor is political.

Since World War II, the National Guard has been deployed only 10 times by presidents, mostly to support desegregation and protect civil rights. All but one of these mobilizations came at the governor’s request — the only exception, before Trump, was President Dwight Eisenhower’s 1957 mobilization of the Arkansas National Guard to desegregate schools in Little Rock at the wishes of Governor Orval Faubus.

In sharp contrast, Trump tried three times to send troops to major cities despite explicit objection from Democratic governors. This is the case in Portland.

The deployment of the National Guard and the constitutional stakes

The lawsuit filed in Oregon says there is no national emergency in the city, and that deploying the Guard to the state without Gov. Tina Kotick’s approval — in fact, over her vocal objection — and absent extraordinary circumstances that would justify federalism under Title X, is illegal. The lawsuit asserts that the National Guard remains a government institution that federal authorities cannot control.

Read more: A lawsuit against Trump’s deployment of the National Guard to Washington exposes the country’s deep partisan divide

The two deployments, in Oregon and Illinois, are making their way through federal courts, and the Trump administration has asked the Supreme Court to intervene to allow the deployments. What the court will do if the cases reach it is uncertain. Roberts has demonstrated a willingness to invoke state sovereignty in some contexts while rejecting it in others.

For now, the Court has upheld many of the Trump administration’s actions while restricting others, suggesting jurisprudence driven more by specific contexts than by categorical rules.

The success of Oregon’s challenge may depend less on the long and changing history of Tenth Amendment doctrine than on how the court views immigration enforcement, presidential power and the consequences for American democracy of Trump’s repeated invocations of emergency power.

This article is republished from The Conversation under a Creative Commons license. Read the original article.