The writer is director of the U.S. immigration policy program at the Migration Policy Institute. She served as commissioner of the U.S. Immigration and Naturalization Service from 1993-2000.

Illegal immigration and enforcement have been the dominant concerns driving immigration policy for more than 25 years. Deep public skepticism over the federal government’s will and ability to enforce the nation’s immigration laws has come with them. As a result, “enforcement first,” a proposition that argued for effective enforcement as a precondition to broader reforms, became widely embraced.

In a report released Monday, the Migration Policy Institute documents how dramatically facts have changed from those long-held perceptions. Particularly since Sept. 11, 2001, but dating to the 1986Immigration Reform and Control Act (IRCA) — which attempted to end illegal immigration through employer sanctions, increased border enforcement and legalization — the nation has made unprecedented, steep investments in the capacity of federal agencies to aggressively enforce immigration laws.

Since the 1986 legislation was enacted, nearly $187 billion has been spent on immigration enforcement. Budgets for the two main federal enforcement agencies — U.S. Customs and Border Protection (CBP) and U.S. Immigration and Customs Enforcement (ICE) — and its primary enforcement technology initiative, the U.S. Visitor and Immigrant Status Indicator Technology (US-VISIT) program, are nearly 15 times what was spent to operate the U.S. Immigration and Naturalization Service in 1986.

Today, the federal government spends more on its immigration enforcement agencies than on all its other principal criminal law enforcement agencies combined. Spending for Customs and Border Protection, Immigration and Customs Enforcement, and US-VISIT reached nearly $18 billion in fiscal 2012. Contrast that with the $14.4 billion spent for the FBI, Drug Enforcement Administration, Secret Service, U.S. Marshals Service and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Such spending — which reflects a strong, pro-enforcement consensus in Congress — has built a muscular, complex, cross-agency system. It extends beyond U.S. borders to screen visitors against multiple intelligence and law enforcement databases before they arrive in the United States. It also reaches into communities across the country through information sharing, interoperable databases and partnerships with state and local law enforcement.

The system that has emerged is generating record levels of enforcement results:

●Customs and Border Protection and Immigration and Customs Enforcement refer more cases for federal prosecution than all the Justice Department law enforcement agencies combined, including the FBI, DEA and ATF.

●A significantly larger number of individuals are detained each year in the immigration detention system (just under 430,000 in fiscal 2011) than are serving sentences in federal Bureau of Prisons facilities for all other federal crimes.

●More than 4 million noncitizens, primarily unauthorized immigrants, have been deported from the United States since 1990, with removals rising from 30,039 in fiscal 1990 to a record 409,849 in fiscal 2012.

●Imperatives for border control have led to record highs in Border Patrol staffing, technology and infrastructure. At the same time, apprehensions have fallen to 40-year lows — 340,252 in 2011, down from more than 1.6 million in fiscal 2000. After the 1986 reforms, growth of the resident unauthorized population resumed and increased to levels of about 525,000 annually. But that began to change in 2007, and there has been a negative flow since. The shift primarily stems from reduced job demand in a recession economy and changing conditions in Mexico, but it also reflects the buildup of enforcement capacities. Together, they have led to a fundamental reset in the calculus of illegal migration.

The nation has built a formidable immigration enforcement machinery. Judging by resource levels, case volumes and enforcement actions, immigration enforcement ranks as the federal government’s highest criminal law enforcement priority. “Enforcement first” has become the nation’s de facto response to illegal immigration. Changes to the immigration system have focused almost entirely on building enforcement programs and improving their performance.

Gaps in enforcement, such as employer accountability, remain to be addressed. But building an ever-larger enforcement bulwark is hard to justify in an era of fiscal restraint and one in which illegal immigration has abated because of factors that include strengthened enforcement and immense resource infusions.

Even with record-setting expenditures and the full use of a wide array of statutory and administrative tools, enforcement alone — no matter how well administered — is an insufficient answer to the broad challenges that illegal and legal immigration pose for America’s future. Changes must also be made to better align immigration policy with the nation’s economic and labor market requirements and with future growth and well-being.

The enforcement machinery that has been built can serve the national interest well if it also provides a platform for policy changes suited to the larger challenges that immigration represents for the United States in the 21st century.