Fact check: Can the marines and national guard work together on a protest by law

1. Summary of the results

The Marines and National Guard can work together during protests, but with significant legal restrictions and only under specific circumstances. Their cooperation is primarily limited to protecting federal personnel and property, and they cannot perform core law enforcement functions like arrests or crowd control ^{[1] [2]}. The primary legal barrier is the Posse Comitatus Act, which generally prevents the U.S. military from conducting law enforcement operations within the United States ^[3].

2. Missing context/alternative viewpoints

Several crucial pieces of context are missing from the original question:

• The Insurrection Act of 1807 is a key legal mechanism that would allow fuller military involvement in domestic law enforcement, but it must be specifically invoked ^{[3] [4]}
• There is a real-world precedent: Marines and National Guard troops have been deployed together in Los Angeles, operating under strict rules of engagement - including unloaded weapons and instructions to avoid crowd engagement unless absolutely necessary ^[5]
• Military personnel are trained for combat, not domestic law enforcement, making their deployment in civilian situations problematic ^[6]
• The Trump administration has federalized the National Guard but notably did not invoke the Insurrection Act ^[7]

3. Potential misinformation/bias in the original statement

The original question oversimplifies a complex legal and operational situation. Several stakeholders have different interests in this matter:

• Military leadership might be concerned about the precedent of using combat-trained forces for domestic operations ^[6]
• Legal experts warn about challenging the traditional separation between military and police forces ^[7]
• Federal government interests are represented through the Patriot Act, which expanded military use possibilities ^[4]
• Civil rights advocates might be concerned about the potential for nationwide military intervention ^[7]

The deployment of both forces together is considered extraordinary and potentially legally questionable ^[8], suggesting that while it can happen, it shouldn't be viewed as a normal or uncontroversial option.