Immigration has been a touchstone of the U.S. political debate for decades, as policymakers must weigh competing economic, security, and humanitarian concerns. Congress has been unable to reach an agreement on comprehensive immigration reform for years, effectively moving some major policy decisions into the executive and judicial branches of government, and fueling debate in the halls of state and municipal governments. Meanwhile, the fates of an estimated 11 million undocumented immigrants in the country, as well as rules for legal immigration, lie in the balance.

The immigration debate moved to the fore once again with the inauguration of Donald J. Trump, who made the issue a centerpiece of his presidential campaign. Shortly after taking office, President Trump signed executive orders on border security, interior enforcement, and refugees, which attempt to follow through on some of his controversial campaign pledges. Some U.S. cities, states, and individuals have challenged the orders in court.

What is the immigrant population in the United States?

Immigrants comprise about 13 percent of the U.S. population: some 43 million out of a total of about 321 million people, according to Census Bureau data from 2015. Together, immigrants and their U.S.-born children make up about 27 percent of U.S. inhabitants. The figure represents a steady rise from 1970, when there were fewer than 10 million immigrants in the United States. But there are proportionally fewer immigrants today than in 1890, when foreign-born residents comprised 15 percent of the population.

Illegal immigration. The undocumented population is about 11 million and has leveled off since the 2008 economic crisis, which led some to return to their home countries and discouraged others from coming to the United States. In February 2017, Customs and Border Protection reported a 36 percent drop in crossings from the year before, which some attribute to the Trump administration’s policies.

More than half of the undocumented immigrants have lived in the country for more than a decade; nearly one-third are the parents of U.S.-born children, according to the Pew Research Center. Central American asylum seekers, many of whom are minors who have fled violence in their home countries, make up a growing share of those who cross the U.S.-Mexico border. These immigrants have different legal rights from Mexican nationals in the United States: under a 2008 anti–human trafficking law, minors from noncontiguous countries have a right to a deportation hearing before being returned to their home countries.

Though many of the policies that aim to reduce unlawful immigration focus on enforced border security, individuals who arrive to the United States legally and overstay their visas comprise a significant portion of the undocumented population. According to the Center for Migration Studies, individuals who overstayed their visas have outnumbered those who arrived by crossing the border illegally by 600,000 since 2007.

Legal immigration. The United States granted more than 1 million individuals legal permanent residency in 2015, nearly two-thirds of whom were admitted based on family reunification. Other categories included: employment-based preferences (14 percent), refugees (11 percent), diversity (5 percent), and asylees (3 percent). In 2016 there were more than 4 million applicants on the State Department’s waiting list for immigrant visas [PDF].

Hundreds of thousands of individuals work legally in the United States under various types of nonimmigrant visas. In 2016, the United States granted [PDF] more than 180,000 visas to high-skilled workers, known as H-1B visas, and more than 200,000 visas to temporary workers in agriculture and other industries. The issuance of new H-1B visas is capped at 85,000 per year.

Immigrants made up roughly 17 percent of the U.S. workforce in 2014, according to Pew Research Center; of those, around two-thirds were in the country legally. Collectively, immigrants made up 45 percent of domestic employees; they also comprised large portions of the workforce in U.S. manufacturing (36 percent), agriculture (33), and accommodation (32). Another Pew study found that without immigrants, the U.S. workforce is expected to decline from 173.2 million in 2015 to 165.6 million in 2035; the workforce is expected to grow to 183.2 million if immigration levels remain steady, according to the report.

How do Americans feel about immigration?

A 2016 Gallup poll found that 72 percent of Americans considered immigration a “good thing” for the United States, and as many as 84 percent supported a path to citizenship for undocumented immigrants if they meet certain requirements. A separate Gallup poll found that among Republicans, support for a path to citizenship (76 percent) was higher than support for a proposed border wall (62 percent).

What legislation has Congress considered in recent years?

Congress has debated numerous pieces of immigration reform over the last two decades, some considered “comprehensive,” others piecemeal. Comprehensive immigration reform refers to omnibus legislation that attempts to address the following range of issues: demand for high-skilled and low-skilled labor; the legal status of the millions of undocumented immigrants living in the country; border security; and interior enforcement.

The last time legislators came close to significant immigration reform was in 2013, when the Democrat-led Senate passed a comprehensive reform bill that would have provided a path to citizenship for undocumented immigrants as well as tough border security provisions. The bill did not receive a vote in the Republican-controlled House of Representatives.

What actions have presidents taken in recent years?

Barack Obama. President Obama took several actions to provide temporary legal relief to many undocumented immigrants. In 2012, his administration began a program, known as Deferred Action for Childhood Arrivals (DACA), that offers renewable, two-year deportation deferrals and work permits to undocumented immigrants who had arrived to the United States as children and had no criminal records. Obama characterized the move as a “stopgap measure” and urged Congress to pass the Dream Act, legislation first introduced in 2001 that would have benefited many of the same people. As of September 2016, more than 750,000 people had taken advantage of DACA.

In 2014, Obama attempted to extend similar benefits to as many as 5 million undocumented parents of U.S. citizens and permanent residents. However, more than two dozen U.S. states sued the administration, alleging that the program, known as Deferred Action for Parents of Americans (DAPA), violated federal immigration law and the U.S. Constitution. A Texas federal judge blocked the program in 2015, and the Supreme Court effectively killed it in 2016.

Donald J. Trump. Trump made immigration and national security signature issues of his presidential campaign, often staking out controversial positions. During his first few weeks in office, he signed several executive orders attempting to follow through on some of his campaign pledges. The first, which focused on border security, instructed federal agencies to construct a physical wall “to obtain complete operational control” of the U.S. border with Mexico. The second, which focused on interior enforcement, broadened definitions of those unauthorized immigrants prioritized for removal, ordered increases in enforcement personnel and removal facilities, and moved to restrict federal funds from so-called sanctuary jurisdictions, which in some cases limit their cooperation with federal immigration officials. This rule also expands the application of “expedited removal” to anyone who cannot prove they have been in the United States for two years, allowing them to be removed without a court hearing. The third, which focused on terrorism prevention, banned nationals from Iran, Iraq, Libya, Somalia, Sudan, and Yemen from entering the United States for at least ninety days; blocked nationals from Syria indefinitely; and suspended the U.S. refugee program for 120 days.

The actions, particularly the ban on travelers from seven Muslim-majority countries, drew widespread protests and legal challenges from individuals, cities, and states. In February 2017, a federal judge in Washington State imposed a nationwide restraining order on the so-called travel ban, ruling that the plaintiff states, Washington and Minnesota, had been injured by it and were likely to win their lawsuit challenging its constitutionality. After an appeals court affirmed the ruling, the Trump administration issued a revised order that, among other things, dropped Iraq from the list of affected countries, removed a provision giving preferential treatment to religious minorities (which was seen by critics as a way to exclude Muslims), and excluded those that already had U.S. visas. Additionally, the ban on Syrians was reduced to 120 days. In March, a federal judge in Hawaii imposed a temporary restraining order on this order.

President Trump lowered the annual cap of refugees admitted to the United States from 110,000 to 50,000, and his orders may also make it more difficult for individuals to seek asylum. According to U.S. figures, more than 83,000 people [PDF], many of whom were unaccompanied minors from Central America, filed for asylum in 2015. The new executive orders call for an amended questioning process for those seeking asylum, intended to vet for “fraudulent answers.” Experts say this change could allow immigration officers to be tougher in interpreting standards for asylum. Parents in the United States who pay smugglers to bring their children north could also face legal action, including deportation, under the executive orders.

How are state and local authorities handling these issues?

States vary widely in how they treat unauthorized immigrants (or anyone suspected of being unauthorized). Some states, like California, allow undocumented immigrants to apply for drivers’ licenses, receive in-state tuition at universities, and obtain other benefits. At the other end of the spectrum, other states, like Arizona, have passed laws permitting police to question people about their immigration status.

The federal government is generally responsible for enforcing immigration laws, but it may delegate some immigration-control duties to state and local law enforcement. However, the degree to which local officials are obliged to cooperate with federal authorities is a subject of intense debate. Proponents of tougher immigration enforcement have labeled state and local jurisdictions that limit their cooperation with federal authorities as “sanctuary cities.” There is no official definition or count of sanctuary cities, but the Immigrant Legal Resource Center identifies more than six hundred counties with such policies.

The Obama administration’s enforcement practices drew criticism from the left and the right. Some immigrant advocacy groups criticized his administration for overseeing the removal of more than 3 million people during his eight-year tenure, a figure that outpaced the administrations of former Presidents Bill Clinton and George W. Bush. Many Republicans said the administration was soft on enforcement in narrowing its removal efforts to undocumented immigrants who have committed serious crimes.

President Trump decried sanctuary cities throughout his campaign and has issued executive orders to block federal funding to such municipalities and to reinstate a controversial program, known as Secure Communities, in which state and local police provide fingerprints of suspects to federal immigration authorities, and hand over individuals presumed to be in the country illegally. He also ordered the expansion of enforcement partnerships between federal, state, and local agencies. Several cities have filed lawsuits challenging Trump’s attempt to block federal funding to sanctuary jurisdictions.

What are the prospects for immigration reform?

Experts say the prospect for comprehensive immigration reform is dim given President Trump’s positions and general political divisions in Washington. “There is no appetite in the Republican party to try to go down the comprehensive [immigration policy reform] road again,” says CFR’s Edward Alden. Some lawmakers may attempt to take a piecemeal approach, starting with enforcement measures, but bipartisan support for “cherry picking” policies is unlikely, he says.

However, one area of immigration policy that could see congressional action is the H-1B program. Democratic and Republican lawmakers have expressed interest in reforming the program, which critics say has been abused by companies to outsource skilled labor and cut costs. In March 2017, the Trump administration announced it would temporarily suspend a program to fast-track H-1B applications.

This backgrounder first appeared Mar. 28 on the Council on Foreign Relations’ website.