The need to build a complete border barrier between the United States and Mexico was a consistent feature of Trump's campaign trail rhetoric. Even after winning the election, Trump continued to tout the wall's necessity. Now, it is well within the new administration's power to seek legal justification and funding to build additional barriers along the border. This could mean additional fencing, but actually building a substantial wall is no small matter. It is relatively straightforward to reinforce places where barriers, such as pedestrian fencing, already exist. But when it comes to the substantial reaches of borderland without fencing, such as the winding path of the Rio Grande as it makes its way through Texas, things become more complicated. It would be difficult for the incoming administration to justify constructing additional barriers along parts of the exposed Texas border, in part because of the natural barrier posed by waterways, and because much of the land along that section is privately owned.
Before initiating the project, Trump's administration would have to get Congress to agree that it has legal authorization for it, and lawmakers would have to approve the significant funding required. It is unclear what kind of project the new administration has in mind, but any attempt to construct new fencing or add barriers would likely face federal court challenges. In a worst-case scenario for the administration, a lengthy legal challenge would have to be resolved before construction could even begin. Local or national groups opposed to building the barrier would line up to seek injunctions preventing its construction, especially along parts of the border not already fenced off. Lawsuits could come even before funding is authorized.
The first challenge for Trump's administration will be to determine the scope of what it wants to attempt. In December, members of the Trump transition team met with the Army Corps of Engineers to discuss the project and with the Department of the Interior to see whether regulations that might hinder construction could be waived. Any effort to build a major barrier will be met with resistance in Congress because lawmakers who have border constituencies will be reluctant to approve a project that would require obtaining land through eminent domain. Another option is to build a reinforced barrier along a relatively short stretch of the border, hoping that the symbolic effort is enough for the Trump administration to say it is fulfilling its campaign promise.
The government actually has a legal basis under which it can claim to Congress that it needs funding for a wall. The 2006 Secure Fence Act led to the construction of about 1,050 kilometers (650 miles) of border fence — half of which is pedestrian fencing, with the other half incorporating barriers to keep vehicles from crossing over. Most of this fencing runs through Arizona, New Mexico and Texas. Border barriers in Texas are mainly limited to high-traffic crossings, such as land adjacent to large border cities. Under the Secure Fence Act and adjustments made to the 1996 Illegal Immigration Reform and Immigrant Responsibility Act, the president has broad powers to determine what kind of border barriers to build and where to build them.
Trump's team will most likely try to make a case for applying the Secure Fence Act's provision for placing barriers "along not less than 700 miles of the southwest border." A 2008 amendment to the 1996 law slightly changed that provision, specifying that the Department of Homeland Security (DHS) can determine where it needs to install such fencing. The Trump administration may also try to rely on Section 102 of the 2005 Real ID Act, which allows the DHS to waive legal requirements to ensure the quick construction of barriers that it is already authorized to build. The administration will almost certainly have to make the case for what requirements should be waived and why. The Trump administration may claim it already has the legal authority to build fencing and could use these two provisions to request funding from Congress. Whether it gets the money is another question. It is clear, though, that the administration has the means to justify its demand for funding a barrier, whether it's a wall, a fence or even just vehicle obstacles.
An attempt to provide funding for construction could come within a year. The House of Representatives and the Senate are slated to vote on a continuing resolution in late April to fund government operations, giving lawmakers in favor of border fence construction a chance to attach a funding authorization to it. Any attempt to shut down a border fence funding initiative added to the budget resolution would lead to a wider battle that could be too politically costly to pursue. Any delays to appropriating money for a border fence project, as well as legal battles that may ensue, could push the building of additional barriers beyond a Trump presidency — a fact that could jeopardize the entire initiative. Trump's successor could choose to defund the initiative or redirect the nature and scope of any construction to differ from its original intent.
The political effects of any new border barrier on U.S.-Mexican relations will be influenced by several factors, including what input Mexico will be allowed to give on the project. Some of Mexico's main concerns about a border wall include whether it reroutes migrants (particularly Mexican ones) to more dangerous border crossings, such as those through the Sonoran Desert; whether it leads to more Central American migrants being bottled up in Mexican states; whether it results in disruptions to commercial cross-border traffic; and whether the United States continues to voice any public demands that Mexico pay for the wall.
The Trump administration is also apparently considering another border policy option, one that would stem the flow of immigrants into Mexico from Central America. The effort would hinge on an initiative to help Mexico bolster security along the Guatemalan border. The main thrust of that option appears to be a joint funding initiative to secure the border, then possibly seeking a reimbursement of that money back from Mexico. Logistically, such an effort would seem to be simpler than constructing a complete wall along the U.S. border, given the relatively shorter distance and the limited number of roads and rail lines crossing from Guatemala into Mexico. But that plan has its shortcomings. Corrupt border officials could facilitate their northward journey, and it could suffer the same potential shortcomings as would a U.S.-Mexico border wall as immigrants find ways to bypass security mechanisms.