On Monday, Mexican cartel members brutally murdered nine members of an American family—three women and six children—in the Mexican state of Sonora, about 70 miles south of Douglas, Arizona.

It was a horrific attack, in which cartel gunmen opened fire on the three vehicles of the Americans, riddling them with bullets and causing one vehicle to explode.

President Trump tweeted on Tuesday morning:

This is the time for Mexico, with the help of the United States, to wage WAR on the drug cartels and wipe them off the face of the earth. We merely await a call from your great new president!

His offer was met with a quick dismissal by Mexican President Luis Obrador, who said, “It’s not in agreement with our convictions. The worst thing is war.”

The carnage in Mexico wrought by the drug cartels has reached previously-unseen levels. In 2018, a record number of 33,341 murder investigations were opened, 33% higher than the previous record set in 2017. Although former Mexican President Enrique Peńa Nieto promised to reduce cartel violence, it actually increased 40% during his tenure. President Obrador took office in December 2018 pledging to use the Mexican military to combat the cartels. But the violence continues. A significant reason why is that the corruption that permeates government throughout Mexico also infects the military. Indeed some cartel members brag about how easily they bribe members of the military.

It has become abundantly clear that Mexico cannot or will not defeat the cartels by itself. And now American citizens are being shot, in addition to the thousands of Americans already killed by the fentanyl, meth, and other drugs smuggled into the United States by the cartels. If U.S policy does not change, the cartel killings will continue, because Mexico has proven itself incapable of defeating the cartels. At some point, the United States has to act to protect the lives of its own citizens.

Taking action without the permission of Mexico would be difficult, given that Mexico is a neighbor and a nominal ally of the United States. And at least on the surface, the Mexican government says it doesn’t want our help. But the case for utilizing the U.S. military has become compelling. In addition, there is a way to change the mind of the Mexican President.

1. The cartels should be designated as terrorist organizations.

In March 2019 President Trump publicly stated that he was considering designating the cartels as international terrorist organizations. He should now do so. According to 18 U.S.C. 2331, such terrorism is “intended (i) to intimidate or coerce a civilian population; [or] (ii) to influence the policy of a government by intimidation or coercion.” The cartels clearly fit within this definition. They have used violence to intimidate government officials and civilians for decades.

Not only do they meet the definition of terrorist organizations, they function as terrorists and are well-outfitted with military weaponry. And they are more powerful than some other terrorist organizations around the world.

2. The cartel-controlled areas of Mexico are de facto narco-states.

By the Mexican government’s own estimation, the cartels now control 57.5% of the country. Earlier this year, the Mexican investigative journal Contralínea posted a map of Mexico created by the Obrador government, showing that 57.5 percent of the districts in the country are controlled by the cartels, and another 23.3 percent are of disputed control. In other words, the cartels exercise either partial or complete control over 80 percent of the country.

In the areas controlled by cartels, the sovereignty of the Mexican government is only theoretical. For example, “El Tena,” who leads a cartel in the Mexican state of Michoacan, travels in a caravan of trucks led by one with a .50 caliber machine gun mounted in the bed. He travels the region with impunity running meth labs and other criminal organizations. He would fit in well with the terrorist warlords of Somalia.

Cartels throughout Mexico are equally powerful. They are well armed, sometimes carrying RPGs and driving custom-built armored vehicles. They often engage and defeat Mexican law enforcement or military units.

When a terrorist organization like ISIS or Al Qaida threatens a country or group that the United States military is protecting, such as the Kurds, we have no hesitation in launching attacks against that terrorist organization—even if it involves operating on another sovereign nation’s territory. We should be equally willing to do the same to protect our own citizens along the Mexican border.

3. The cartels have already invaded and occupied U.S. territory.

Most Americans would likely be shocked to learn that these terrorist organizations have occupied strategic territory within the United States for years. Heavily-armed cartel scouts occupy hilltops along the border in New Mexico and Arizona. They monitor the movements of the Border Patrol and direct their own smugglers when and where to bring in the drugs. Some hilltops are occupied 24/7.

Every once in a while, U.S. law enforcement is able to make a move on these scouts and arrest them. But doing so is extremely dangerous, and more like a military operation than a routine law enforcement arrest. But there has been astonishingly little coverage of the fact that these cartels operate on, and control, U.S. territory.

If an armed foreign terrorist organization penetrated U.S. territory and occupied strategic locations, most people would call that an invasion. That’s exactly what we have. And such an invasion entirely justifies a military response. The safety and sovereignty of the United States is at stake.

4. It’s time for a real quid pro quo.

The United States has given the Mexican government more that $2.5 billion dollars in military and non-military aid since the “Merida initiative” began in 2008. In 2018 alone, we gave Mexico nearly $88 million in aid.

The time has come to put strings on that money. It has accomplished little to date. And we are borrowing from the Chinese to give Mexico the money. We cannot continue to subsidize a foreign military that fails to keep U.S. citizens safe. The United States should tell the Mexican government that all American aid will end unless the Mexican government permits the U.S. military to conduct limited operations on both sides of the border to crush the cartels. We don’t need permission to operate in all of Mexico, but we need to ensure that the cartels no longer operate with impunity in the regions near the U.S. border.

The U.S. military strikes would have to be surgical, ideally by drones in most cases and by special forces when necessary. Civilian casualties would have to be avoided at all cost. But even under those constraints, the U.S. military could exert devastating force against the cartels and their leadership. Enough is enough. We routinely use the U.S. military to defend the citizens of other nations abroad. It’s time to use our military to directly defend the United States and its citizens.

Kris W. Kobach served as Secretary of State of Kansas during 2011-19. An expert in immigration law and policy, he coauthored the Arizona SB-1070 immigration law and represented in federal court the 10 ICE agents who sued to stop Obama’s 2012 executive amnesty. He is now General Counsel of We Build the Wall and is a Republican candidate for Kansas’s open U.S. Senate in 2020. His website is kriskobach.com.