With a few words to Glenn Beck last week, Scott Walker busted open the conservative debate on immigration.

The Wisconsin governor and possible presidential candidate called for a "legal immigration system that's based, first and foremost, on protecting American workers and American wages." His remarks were widely circulated by Breitbart's doggedly anti-amnesty reporter Matthew Boyle. Then the internet exploded, with some of the strongest negative reactions coming from my fellow conservatives.

Note that Walker, whose position on whether he would offer legal status to illegal immigrants is famously murky, stops short of actually calling for a lower level of legal immigration. But he does invoke Alabama Sen. Jeff Sessions, the most prominent Republican who is calling for curbing immigration.

The political ramifications of Walker's comments are unclear. He appeared to cut against things he's said about immigration in the past, and certainly contradicted the preferences of major Republican donors, including the otherwise Walker-friendly Koch brothers. But Walker's concern about immigration and wages comes as polls for the first time show him losing his grip on conservatives to candidates who are theoretically vulnerable on immigration.

The contours of the conservative debate on immigration are relatively clear. To conservatives who disagree with the sentiments Walker expressed, our current immigration policy is like free trade. Lowering immigration levels to protect American wages is like protectionism, they argue. If anything, they say, our immigration caps are already too low and account for why there is so much illegal immigration.

Plenty of conservatives who agree with Walker and Sessions don't care much for free trade either. But many of us who aren't trade protectionists nevertheless think the trade/immigration analogy is flawed. People are different than goods, even if labor is a commodity. An employer gets an immigrant's labor, but America gets the whole person.

Immigration is not just about economics. It involves citizenship, a membership in the American nation-state based on criteria defined by the broader political community. When there is no citizenship, as is the case with various guest-worker programs, you get laborers who are heavily dependent on their employers and effectively denied membership in the political community.

"One of the worst things about illegal immigration is that it creates a class of people who contribute their labor to this country but aren't full participants in it and lack the rights and responsibilities of everyone else," writes Ramesh Ponnuru. "A guest-worker program doesn't solve this problem. It formalizes it."

Plus, a lot of people who cite market forces in their conservative immigration arguments are missing the bigger picture. As David Frum notes in The Atlantic, we seldom hear the following immigration scenarios:

"If we admit a lot of foreign-born surgeons, we could hugely drive down the cost of major medical operations. American-born doctors would shift their labor to fields where their language facility gave them a competitive advantage: away from surgery to general practice. This policy would hugely enhance the relative purchasing power of plumbers and mechanics, enabling them to eat out more often and buy more American-made entertainment, increasing GDP and creating jobs."

Or: "The ratio of CEO pay to other workers has skyrocketed. Obviously we are suffering from a glut of workers and massive CEO scarcity. We should issue work permits automatically to any executive with a job offer that pays more than $500,000 a year. Americans with organizational skills will be pressed to shift to the public sector, improving the quality and lowering the cost to taxpayers of government services." [The Atlantic]

And yet, these same theories are deployed in defense of immigration — because it enhances labor competition at the middle and lower rungs of the economic ladder.

Maybe our immigration policy is less like free trade than corporate welfare. Dave Brat made this argument en route to defeating Eric Cantor, the sitting House majority leader, in a Republican primary last year. And it's not hard to see why this view is appealing to conservatives.

Immigration's impact on American jobs and wages is hotly contested. But the arguments Walker is starting to entertain are at least as plausible as Jeb Bush's plan to have immigrant workers finance the baby boomers' retirement. This is a debate conservatives need to have. Is immigration like free trade, corporate welfare — or something much bigger than either?