‘Comprehensive immigration reform,” a deal on which is reportedly imminent, has a lot of moving parts — too many, in truth, as with most “comprehensive” legislation. Among the costs of comprehensivism is that debate over such bills often gets bogged down in the many details. Americans seeking to evaluate any deal should ask three questions about it to cut through the noise. First: Will it encourage future illegal immigration? This has always been the greatest risk of proposals to provide legal status for current illegal immigrants: that it will be seen as a reason for others to come here illegally...