I've heard this argument that only the federal government has the power to enforce immigration but this is false. The federal government could have the power to do that but just because the federal government has the power to do something doesn't mean that the states lose that same identical power. There are a few powers that are exclusive to the federal government such as the power to declare war on a foriegn nation. This power is granted to the federal government but is also denied to each state. That makes it an exclusive power of the federal government. What made that power exclusive to the federal government was that it was granted that power and the states were denied it. Immigration (nor naturalization) not specifically denied to each state so any state can enforce its own immigration laws as it sees fit in conjunction with the federal government or against it.