Some lessons, even though they involve national security, are never learned.

In Europe and America, open borders have facilitated terrorism. Failed immigration policies have invited terrorists to set up shop on both sides of the Atlantic, and carry out their murderous plots.

The 9/11 attacks provide the most dramatic example of the United States’ immigration failures. Foreign nationals from Saudi Arabia, the United Arab Emirates, Egypt and Lebanon relied on several different flawed immigration programs. A Center for Immigration Studies report found that Islamic militant terrorists used student, tourist and business visas, which several overstayed, and also committed marriage and passport fraud to enter and remain in the U.S. as they conspired to murder. Many terrorists had lived in the U.S. long enough to become legal permanent residents or citizens.

More recently, former FBI director James Comey said that inadequate refugee vetting simplifies terrorists’ entry. Last year, the Senate Subcommittee on Immigration and the National Interest confirmed Comey’s statement when it identified what it called a “partial” list of 30 admitted immigrants implicated in terrorism activities. The list includes several who, like the 9/11 terrorists, had permanent resident or citizenship status, most notably, Pakistani Tashfeen Malik who with her husband perpetrated the 2015 San Bernardino massacre that left 14 dead and 22 seriously injured.

Despite numerous warning signals post-9/11 that more cautious immigration policies are essential, in 2009, the Defense Department created the Military Accessions Vital to the National Interest (MAVNI) program that allowed more than 10,000 foreign-born enrollees to join the U.S. armed forces.

In concept, the foreign nationals would bring special skills or talents to the military not otherwise available to it. In exchange for their military service, immigrants would receive expedited citizenship. Advocates often argue that immigrants will do jobs that Americans can’t or won’t do, one of MAVNI’s selling points.

Now that MAVNI has an eight-year track record, uncomfortable realities about its risks have emerged. Details are still emerging, but the Pentagon’s Inspector General’s year-long analysis uncovered “potential security risks” that include foreign infiltration, a thinly veiled terrorism reference. And, no surprise to immigration critics, MAVNI eventually enrolled low-skilled workers like cooks, drivers and mechanics.

The whereabouts of some MAVNI participants are unknown; the Defense Department won’t answer questions about their possible location, and the program is not processing new applications.

Retired U.S. Army General Jack Keane, who contributed to an exclusive Fox News story, said that ISIS depends on migration as a way to carry out terrorism in Europe, and without proper vetting will do more of the same domestically. U.S. Rep. Steve Russell (R-Okla.), also a retired Army officer who sits on the House Armed Services military personnel subcommittee, said that MAVNI is “replete with problems.”

MAVNI is the latest example of how expanded immigration puts Americans second. Since the 1965 Immigration and Nationality Act, the common denominator in immigration legislation is more – more amnesties, more employment-based visas, more refugees, and more immigrant entitlements. More immigration displaces U.S. workers, and the MAVNI cooks, drivers and mechanics that took jobs Americans would have done are good examples of that. And, more immigration compromises national security.

Less immigration, unpopular on Capitol Hill but in Americans’ eyes a priority, is long overdue.

Joe Guzzardi is a Californians for Population Stabilization Senior Writing Fellow. Contact him at joeguzzardi@capsweb.org. Follow him on Twitter @joeguzzardi19.