Donald Trump's threat to invoke the Insurrection Act against Minnesota protesters has puzzled European audiences. The confusion is structural rather than political.
The United States retains legal tools for domestic military deployment that European democracies deliberately dismantled during the 20th century. That difference matters because the transatlantic alliance rests on shared assumptions about civilian control, legality, and restraint.
The Pentagon has placed active-duty units on alert, making this a real-time stress test rather than a hypothetical comparison.
The Insurrection Act grants the US president authority to deploy federal armed forces domestically. It allows military deployment in three scenarios: at a state's request to suppress insurrection; when "unlawful obstructions" render federal law unenforceable; or when rebellion obstructs civil rights protections.
The law imposes few statutory constraints.
The president decides unilaterally what constitutes an insurrection. No congressional approval required. Invoking it can open a legal pathway for federal troops to support, and in some circumstances perform, domestic enforcement functions that would otherwise be constrained by the Posse Comitatus Act.
The Brennan Center documents 30 invocations in 230 years. It was last used in 1992 during Los Angeles riots; it was last deployed without state consent in 1965.
Trump has repeatedly threatened deployment in response to protest unrest, including recent statements regarding Minnesota.
No functional equivalent exists in the European Union's legal framework, nor in most member state constitutions.
The Common Security and Defence Policy explicitly limits EU military operations to external deployment. Member states contribute forces for overseas missions through voluntary arrangements under European Council oversight.
Internal security remains a national competence, exercised through civilian police forces.
For many Europeans, order is something the police restore under law, not something the army imposes under executive will.
EU member states built constitutional architecture to prevent what the Insurrection Act enables.
Germany's Basic Law Article 87a permits Bundeswehr deployment only "for purposes of defence." Domestic use is permitted only under tightly-defined constitutional thresholds, including catastrophic emergencies or threats to the democratic order.
France maintains Operation Sentinelle — approximately 7,000 troops protecting sensitive sites from terrorism. They do not operate as police. Policing powers remain with internal security forces. Expansion requires legal authorisation and parliamentary oversight.
European policing can be heavy-handed, and riot control sometimes involves paramilitary equipment, but the constitutional boundary separating armed forces from domestic order maintenance remains intact
These restrictions reflect deliberate design. European democracies experienced military coups and authoritarian collapse within living memory. Constitutional reforms prioritized civilian primacy.
European internal security follows consistent principles: police primacy, democratic oversight, and proportionality.
Civilian police handle law enforcement. Gendarmerie forces in France, Carabinieri in Italy maintain military organisation but perform civilian policing under interior ministry authority.
European policing can be heavy-handed, and riot control sometimes involves paramilitary equipment, but the constitutional boundary separating armed forces from domestic order maintenance remains intact.
Deployments are typically bounded by statutory authorisation and subject to parliamentary and judicial review. Venice Commission standards mandate emergency powers be necessary, proportional, temporary, and subject to scrutiny.
Security forces use minimum necessary force. In most member states, public-order policing is designed as a civilian function, governed by proportionality doctrines and judicial review.
No European democracy treats military suppression of protests as a routine executive prerogative.
But European audiences should not dismiss Trump's rhetoric as American peculiarity. Three implications warrant attention.
First, emergency powers reveal democratic resilience. Recent National Guard deployments have triggered legal pushback.
In September 2025, a federal judge found aspects of the Los Angeles deployment crossed legal lines associated with the Posse Comitatus Act, illustrating how emergency posture can blur civil-military boundaries.
The gap between US and European frameworks reflects different constitutional settlements on executive authority versus parliamentary control. Trump's threats test whether norms constraining presidential power remain effective without formal legal barriers.
Second, alliance dynamics shift when partners face internal instability. The Pentagon placing active-duty units on alert shows domestic military deployment is not merely rhetorical.
European defence planners monitor these developments because civil-military ambiguity in Washington becomes an alliance variable affecting predictability and operational coordination.
If US forces deploy against civilian protests, European governments must assess implications for security cooperation, not from moral judgment but from institutional clarity about partner reliability.
Third, patterns of democratic erosion tend to travel.
The use of emergency powers to sidestep normal democratic processes — whether migration enforcement, protest suppression, or political intimidation — normalises tools that authoritarian-leaning governments elsewhere study and adapt.
When the United States exercises broad executive discretion in ways European constitutional systems explicitly prohibit, it reduces American capacity to set democratic standards and weakens leverage in diplomatic exchanges over rule of law.
Europeans struggle interpreting Trump's Insurrection Act threats because of structural differences.
European democracies constructed constitutional firewalls separating the military from domestic law enforcement. The United States retained broad executive discretion to deploy armed forces internally.
Both systems face democratic pressures.
European frameworks constrain executive action through parliamentary oversight and judicial review. American frameworks rely more on norms and restraint.
Trump's willingness to threaten military deployment exposes how fragile norm-based constraints become when executives reject them.
For European observers, the lesson is institutional design. Democratic safeguards require legal architecture, not just political culture. When allies cannot read each other's domestic red lines, trust erodes.
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Miro Sedlák is a doctoral candidate in security and defence studies at the Armed Forces Academy of General M. R. Štefánik in Slovakia.
Miro Sedlák is a doctoral candidate in security and defence studies at the Armed Forces Academy of General M. R. Štefánik in Slovakia.