Cycles of fear over perceived undesirables have fueled a thickening entanglement between immigration and criminal law in the United States. Surging criminalization and prosecution of immigration violations, expanding crime-related bases for exclusion and deportation, and the broadening powers to detain and investigate have reshaped the criminal law’s connections to immigration. Immigration law has increasingly permeated and permuted criminal law and procedure. Conversely, criminal-law consequences have transformed civil immigration law. Courts have pushed back on some of the dangers of fierce popular passions in the criminal immigration context. Ultimately, however, the future of this murky and precarious domain depends on finding a way to bridge fierce divides in the political branches.