Local police don’t enforce immigration laws because it’s against the law

The short answer is because they are generally not allowed to. Let me explain.

At the federal level, there is a U.S. Supreme Court decision in Arizona v. United States (2012), which affirmed that immigration enforcement is primarily the federal government’s responsibility. States cannot enforce federal law on their own.

It makes sense if you think back to why the Constitution was created in the summer of 1787. The federal government was weak under the Articles of Confederation. The founders decided that a strong federal government was needed and only the federal government should have the power to declare war, print money, and conduct foreign policy, etc. It was decided the states cannot do the federal government’s duties. This is a main reason for having a constitution — to separate federal and state power and responsibilities.

But you are thinking… “The illegals break the law! Arrest them! Deport them!”

Consider this: Local and state government are generally not allowed to enforce federal law any more than the federal government can enforce state law.

For example, did you know the FBI cannot give you a speeding ticket? It’s true. They don’t have the authority to enforce state law; it isn’t their job. Likewise, the state law enforcement agencies cannot enforce federal law; it isn’t their job, consistent with Arizona v. U.S. (2012).

Here in Massachusetts, we also have the state Supreme Judicial Court decision called Lunn v. Commonwealth (2017), which is consistent with the SCOTUS Arizona (2012) decision. Lunn affirms that Massachusetts local and state law enforcement are not allowed to hold a detainee ‘solely on the basis’ of immigration status. Other states may have something similar to Lunn at the state level.

This also means that once an immigration violator posts bail for their state offense or their state sentence for a state crime has expired, they must be released – we are not allowed to hold them ‘solely on the basis’ of immigration status. 

Local and state police can arrest anyone (including immigration violators) for state offenses but cannot detain/arrest anyone ‘solely on the basis’ of immigration violation. The Massachusetts Chiefs of Police Association and the Massachusetts Sheriffs’ Association are in agreement on this and follow the Lunn decision.

Trump appointed U.S. Attorney Leah Foley told us 14 Massachusetts sheriffs on March 12, 2025, at our monthly sheriffs meeting in Hampshire County, “you are bound by state law.”

We cannot do federal immigration enforcement.

There is an exception.

You may have heard of “287(g).” This is a section of U.S. law that essentially allows a contract to be drafted between local and state law enforcement. This contract allows for the training and deputizing of local and state law enforcement to do federal immigration. This is permissible under Arizona (2012) and Lunn (2017).

Out of the 3,081 sheriffs in the U.S., (last time I checked) only about 80 have a 287(g) contract. Out of the approximately 19,800 police departments and 50 states, only about 1,300 have a 287(g) contract. Most sheriffs and local police departments don’t have a 287(g) contract. The reasons why they don’t vary — i.e. staffing shortages, ideology, legal liability, etc.

Doing citizen crowd control or arresting people who riot is in the purview of local and state police.

Arresting or detaining immigration violators “solely on the basis” of immigration status is not allowed without a 287(g) contract.

So, when you hear people saying that local police, state police, or sheriffs should enforce federal immigration laws, without a 287(g) contract, they are not legally allowed to.

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