Why would a state encourage illegal immigration over the opposition of its citizens? According to the theories of immigration and citizenship, we should expect exactly the opposite: that states will monitor, control, and restrict illegal immigrants' access to citizenship on behalf of its citizens, as has been the experience of most countries. I use my research on Filipino immigration to Sabah, Malaysia to show how Malaysia utilizes census practices and documentation to incorporate an illegal immigrant population from the Philippines. Illegal immigrants play an electoral role in Sabah because of the loosely institutionalized nature of citizenship, a feature common to many other developing countries. Our examination of Malaysia reveals several elements of illegal immigration and citizenship that are common to migratory flows in other developing countries. I conclude by showing how this case is generalizable and what it tells us about illegal immigrant participation in the international system.