Tea Partiers, of all people, should understand this concept: The federal government’s resources are limited and should be focused on its core duties of administering justice and protecting basic rights. In that light, the Obama administration made a sensible decision this week to concentrate on deporting illegal immigrants who threaten the health and safety of Americans.

At the latest count, there are still 11 million people living in the United States without government authorization. The government would be incapable of deporting them all, and even if it could, it would cause tens of billions of dollars in damage to the American economy, as Cato research has demonstrated. Even the 300,000 illegal immigrants currently being processed through the deportation pipeline are clogging the system and drawing resources away from more important business.

In a letter to Senate leaders, Department of Homeland Security (DHS) Secretary Janet Napolitano said the administration would from now on concentrate on deporting those in the system who have committed serious crimes or who have any connections to crime or terrorism. As the secretary explained:

From a law enforcement and public safety perspective, DHS enforcement resources must continue to be focused on our highest priorities. Doing otherwise hinders our public safety mission—clogging immigration court dockets and diverting DHS enforcement resources away from individuals who pose a threat to public safety.

That sounds pretty reasonable. The flip side of the policy change is that hundreds of thousands of peaceable, otherwise normal immigrants who are working and studying in the United States without the right documentation will be allowed to stay and possibly even apply for legal status. Included in this group are undocumented spouses of U.S. military personnel, immigrants who were snared in the system when they actually reported crimes to police, and students who came to the United States as young children with their undocumented parents—students who would be eligible for legal status should Congress pass something like the DREAM Act.

Conservatives such as Rep. Lamar Smith (R-Texas) complain that the administration should be enforcing the law rather than ignoring it, but as I’ve argued for long time, the law as it is currently written is unenforceable and needs to be changed.