President Trump’s executive order Wednesday, mandating the construction of a wall on the U.S. border with Mexico, is a strange milestone—the validation of the central proposal of his campaign, one that has been roundly dismissed by experts as pointless, ineffective, and wildly expensive.

But while Trump can achieve much by simple executive orders, the order on the wall offers little in the way of clarity. Wednesday’s order is really just a set of instructions for Secretary of Homeland Security John Kelly. The American public still doesn’t know how big the wall will be, when it will be built, or how it will be paid for—to pick only the most glaring questions.

The executive order the president signed today touches on several areas of immigration policy and border security. Let’s look at the relevant ones on the wall:

Sec. 2.  Policy.  It is the policy of the executive branch to:

     (a)  secure the southern border of the United States through the immediate construction of a physical wall on the southern border, monitored and supported by adequate personnel so as to prevent illegal immigration, drug and human trafficking, and acts of terrorism;

   (e)  "Wall" shall mean a contiguous, physical wall or other similarly secure, contiguous, and impassable physical barrier.

So far this is clear enough. At times during the campaign, Trump supporters suggested that rather than build an actual physical barrier, he might create a “virtual” wall, or some sort of digital-surveillance mechanism. The order declares a policy that it’s a physical barrier, though that could change. But as the order itself mentions, this is ostensibly already the law of the land, under the Secure Fence Act of 2006. However, an alteration to that law a year later gave the Department of Homeland Security discretion to not build the fence in places where it deemed in unnecessary.

That means the president can order DHS to interpret the law in accordance with his desire to cover the whole border. What the executive order mainly does is to instruct the Kelly to figure out the tough details:

Sec. 4.  Physical Security of the Southern Border of the United States.  The Secretary shall immediately take the following steps to obtain complete operational control, as determined by the Secretary, of the southern border:

     (a)  In accordance with existing law, including the Secure Fence Act and IIRIRA, take all appropriate steps to immediately plan, design, and construct a physical wall along the southern border, using appropriate materials and technology to most effectively achieve complete operational control of the southern border;

     (b)  Identify and, to the extent permitted by law, allocate all sources of Federal funds for the planning, designing, and constructing of a physical wall along the southern border;

     (c)  Project and develop long-term funding requirements for the wall, including preparing Congressional budget requests for the current and upcoming fiscal years; and

     (d)  Produce a comprehensive study of the security of the southern border, to be completed within 180 days of this order, that shall include the current state of southern border security, all geophysical and topographical aspects of the southern border, the availability of Federal and State resources necessary to achieve complete operational control of the southern border, and a strategy to obtain and maintain complete operational control of the southern border.

In essence, then, Trump has announced his intention to follow the law of the United States. But the approach paves the way for Trump to alter the promises he made on the campaign trail in significant ways.

For example, could Trump (by way of Kelly) deem the existing border fence to comply with the law? That would ensure that he has a huge jumpstart on the project. Although he often talked about how tall the wall would be and what it would look like—generally somewhere in the range of 50 feet tall, and made out of solid concrete—Kelly could come back and suggest that was unnecessary or, as experts have argued time and again, impossible. One imagines that Trump would need to build at least a few miles of 50-foot concrete wall for the photo ops, but why bother building the rest when you can declare the promise kept and move on?

Declaring victory might be an alluring strategy for Trump more broadly on immigration. Illegal border crossings are already at historic lows; there were fewer apprehensions of unauthorized crossers at the southern border in 2015 than at any time since 1972. (Experts generally attribute this fluctuation not to American policy but to economic conditions in home countries of would-be migrants. Given that Trump’s ascent has sent the peso into a tailspin, however, that might encourage more attempts.) Deportations are similarly already in progress. Barack Obama deported millions of people, a fact that sometimes flew under the radar but was not lost on Trump himself.

That would also help Trump get off the hook for paying for the wall, a matter that is similarly unresolved by the order. Set aside the question of who will pay: How much will they pay? Trump has suggested a tag of $8 to $12 billion. Other estimates cluster around $15 to $25 billion, with some even higher. It’s up to Kelly to figure that out. Setting aside the late Senator Everett Dirksen’s famous quip, “A billion here, a billion there, pretty soon, you're talking real money,” that’s not a figure that Kelly is likely to come up with by simply juggling DHS’s budget, especially given all the other enforcement priorities Trump has laid out for the department in the executive order.

Trump continues to insist that Mexico will eventually pay for the construction, despite Mexico’s flat refusal. This does actually follow what Trump said during the campaign—he said the U.S. would front the money, and then Mexico would reimburse the U.S. Treasury. He also offered a plan for that, which involved cutting off remittances by unauthorized immigrants to Mexico; jacking up tariffs, which would currently violate NAFTA; cutting off visas to Mexicans; or increasing visa fees. As CNBC reported, there are reasons to doubt this would work to get Mexico to cough up.

In the interim, however, the U.S. still has to find some way to pay for the wall upfront. Members of Congress in both parties have expressed reservations about shelling out billions of dollars for a wall. Congress could raise taxes to pay for it, but that’s deeply unpopular with members, and often with voters. Congress could cut funding from other programs, but taking money away from other programs has a way of eliciting public ire. Or they could simply run up the deficit, which Republicans tend to view as unacceptable during Democratic administrations and more or less fine during Republican ones. So far, the Trump administration has had good luck bending the GOP-led Congress to its will.

For now, all of these questions are just as speculative as they were Wednesday morning. Trump has reaffirmed his intention to build a wall, but in most respects his signature policy remains as vague, and perhaps even vaguer, than it was during the presidential campaign—despite his affixing his signature.


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