President Trump likes to say that he doesn't want to announce in advance when he's going to launch an attack. But on Tuesday, he signed an executive order that did just that.

While on a visit to the headquarters of Snap-On Tools in Kenosha, Wisconsin, the president ordered an interdepartmental review of the H-1B visa program, which allows companies to bring "skilled" foreign workers to fill jobs in the US for a few years. Administration officials have made it clear that "review" means they expect Cabinet officials to suggest changes to the program — either by way of regulation or by asking Congress to pass a bill — in the name of better protecting American workers.

In Kenosha, Trump drew a bright line on the H-1B visa: It "should include only the most skilled and highest-paid applicants and should never, ever be used to replace American workers."

A review of the H-1B program was one of many provisions included in a potential executive order drafted during the presidential transition, which would have taken much more aggressive steps to limit a broad array of work visas. Since arriving in office, however, the Trump administration appears to have focused its efforts on the H-1B program, which awards 65,000 visas a year to people with "highly specialized knowledge" (in practice, jobs requiring at least a bachelor's degree, and often involving technology).

The administration, following Trump's rhetoric on the campaign trail (and that of some populists like current Attorney General Jeff Sessions), has portrayed the H-1B program as a way for unscrupulous business owners to hire cheap foreign labor, rather than hiring qualified American workers or training US citizens for high-skilled jobs.

Over the past few weeks, the administration has suspended a practice that allowed employers to get their applications processed within six weeks (instead of several months) if they paid a higher fee, and issued a warning on the day visa applications opened for 2018 that the government would be cracking down on employers who used H-1B workers for jobs Americans could fill. And now, with this executive order, it's declared that the H-1B visa is a top enemy of the pledge to "Hire American."

The executive order doesn't change H-1B policy on its own, and it doesn't set a timeline for when the review will be completed.

The administration has already hinted at some of the changes it would like to see: It might try to change the existing way the government defines the "prevailing wage" in an industry (the de facto minimum wage for an H-1B visa holder in that industry) and might start handing out H-1B visas for the highest-paid jobs and best-educated employees rather than giving any applicant who meets the basic requirements for the visa a chance.

It's not clear whether it will try to make those changes as regulation (and whether that could survive a legal challenge). Fundamentally, though, the administration is going to have to decide what kind of high-skilled visa program it wants.

If Trump wants to make it harder for outsourcing firms to use H-1Bs to staff call centers, and make it easier for tech giants such as Google and Microsoft to bring over high-level engineers, he could find a surprising amount of bipartisan agreement. But if he wants to follow the lead of chief strategist Steve Bannon and Attorney General Sessions, and crack down on H-1B visas across the board in the name of protecting American "civic society" (in Bannon's words), he'll be gratifying the narrow populism of his most ideological supporters.