Lawmen are worried that the cartel tunnel-builders on the Mexican border are now using their engineered concoctions to smuggle illegals, not merely drugs.

That's what the Daily Caller has found, describing the new anxiety as one was discovered over the weekend, catching about 30 illegals coming in from Mexico and China:

It is not uncommon for agents to find subterranean tunnels along the U.S.-Mexico border, especially in California and Arizona, however, this specific type of tunnel was a rare find:

While subterranean tunnels are not a new occurrence along the California-Mexico border, they are more commonly utilized by transnational criminal organizations to smuggle narcotics. However, as this case demonstrates, law enforcement has also identified instances where such tunnels were used to facilitate human smuggling.

What concerns U.S. officials about human smuggling tunnels is that they leave the U.S. particularly vulnerable to infiltration by Islamic terrorists and other dangerous criminals.

It signals that Mexico's cartels and criminal gangs are innovating, a sure sign that they expect a border wall to go up and of their own intentions to evade it.  There's already big money to be made in human smuggling – about a third of cartel profits as it is – so more so now that it's growing more difficult to get in illegally with the border crackdown.

It's also opened up new avenues for terrorists, who can freely move in and out between borders if they get wind of a tunnel and the U.S. doesn't.  We all know of cases in Europe where terrorist perpetrators have used the fluid borders of the European Union to evade capture for their crimes.  We may be seeing the same thing here if the borders are not sealed shut.

On the illegal alien side of the equation, it means that perhaps the real way to border enforcement isn't in physical barriers, whether of tunnels or walls, but in keeping illegals out of the workforce through E-Verify and raid enforcement mechanisms, and keeping green cards and citizenship off limits except through legal channels under one set of laws for all applicants.

On the terrorist side of the equation, it means that new developments in anti-tunnel technology to detect these illegal pathways must be accelerated and deployed just as surely as the wall's construction must be.

Apparently, it is going to take more than just a wall to gain control of U.S. borders.