The debate over immigration reform, intensified by the surge of unaccompanied child migrants at the U.S.–Mexico border, has many conservatives worried. Republican strategist Lanhee Chen explained that conservative opposition to immigration reform in the United States “is a very visceral reaction to what America should be about.” According to conservative opponents of immigration reform, immigrants will change America.

Reforming our immigration system to allow more immigration would indeed mark a significant change. But far from representing a liberal diversion from American principles, such reform would marginally change America back to the way it used to be.

It’s important to understand how America’s immigration laws have changed over time. The first naturalization law, passed in 1790, did not put any restrictions on immigration. It wasn’t until 1882 that Congress, in its first major legislative restriction, passed a blanket ban on Chinese immigrants. Over the next 40 years, Congress passed laws banning immigration of the Japanese and illiterates, and it imposed low quotas on immigration from European countries whose members were supposedly “unassimilable” — all at the insistence of nationalists, labor unions, progressives, and eugenicists.

Few people would argue for a return to the completely free immigration system set up by the Founders, or for the kind of restrictions that existed in the late 19th and early 20th centuries. Sensible approaches to immigration, however, are to be found in our not-so-distant past.

During the 1950s, the Bracero guest-worker visa program channeled migrants into a legal and regulated market, shrinking the illegal-immigrant population by 90 percent. The Border Patrol handed visas to migrant workers when they entered and sometimes even gave illegal immigrants work visas after they were discovered working on American farms. Instead of building fences or putting troops on the border, the Bracero program welcomed migrants willing to work in the legal migration system of the time. Such a system does not exist today.

Some small reforms and a few tweaks to our current system — such as allowing migrant workers to easily switch jobs, removing quotas, removing or streamlining minimum-wage regulations that apply to migrants, and allowing more sectors of the economy to hire migrant workers — could recreate a workable migration system like the one we had in the heyday of the Eisenhower administration.

Conservatism is not an ideology that opposes all change. It is a reformist ideology that supports measured and practical changes based on our experiences, history, and institutions. It opposes social experiments that radically depart from the past but seeks to adjust our laws to better fit the realities of today, with a firm grounding in our institutions and traditions. Such a pragmatic and measured approach should lead conservatives to support immigration reform — at least in the direction of allowing more lawful immigration and guest-worker visas.

The immigration restrictions of the late 19th and early 20th centuries were a vast social-engineering experiment that departed from America’s traditional open immigration policy. In contrast, allowing immigration to mostly be guided by the market would be a rejection of the social-engineering impulse that arose out of the Progressive era.

Those restrictions caused the percentage of the country that was foreign-born to fall from around 14 percent in 1920 to 4.4 percent in 1965. Falling immigration levels over that period allowed for mass unionization, and, as historian Vernon M. Briggs Jr. argues, thereby enabled the New Deal and Great Society programs to be enacted.

Furthermore, opponents of immigration reform should consider that from 1860 to 1920 about 14 percent of America’s population was foreign-born — compared with 13 percent today. American institutions and traditions aided in the assimilation of immigrants and their descendants in the past. The fast rate of cultural, linguistic, and economic assimilation among today’s immigrants found by Duke University’s Jacob Vigdor indicates that those American institutions and traditions of assimilation are thriving — even for the 11 to 12 million illegal immigrants here.

Conservatives who oppose deregulating the immigration system have some allies on the other side of the political spectrum. While America’s labor unions support legalizing the unlawful immigrants already here, they have supported even more restrictions on future migration of workers. Unions can bargain only by limiting the supply of workers available to employers, which is the root of their longstanding opposition to looser immigration policies.

American history and the opposition to worker migration from the Left indicate that the conservative approach to reforming immigration should be to deregulate worker migration to allow more workers to come legally.

Such an approach has two benefits. The first is that it drives a wedge between Democratic politicians, who want to liberalize future immigration, and their labor-union supporters, who want to further restrict immigration. The second is that it embraces the most important aspect of America’s traditional immigration system: the principle that this country is willing to accept immigrants who will work.

Increasing immigration levels would be a return to the status quo that reigned for most of our nation’s existence. Rather than opposing this return to normality, conservatives should embrace it and push for deregulation that allows foreign workers to legally migrate here.