The Department of Homeland Security has just released new " Policies for the Apprehension, Detention, and Removal of Undocumented Immigrants." Designed to fill in the details after President Obama's announcement that at least four million currently illegal immigrants will be given work permits, Social Security numbers and protection from deportation, the DHS guidelines are instructions for the nation's immigration and border security officers as they administer the president's directive.

The new priorities are striking. On the tough side, the president wants U.S. immigration authorities to go after terrorists, felons, and new illegal border crossers. On the not-so-tough side, the administration views convicted drunk drivers, sex abusers, drug dealers, and gun offenders as second-level enforcement priorities. An illegal immigrant could spend up to a year in prison for a violent crime and still not be a top removal priority for the Obama administration.

In the memo, DHS Secretary Jeh Johnson says his department must develop "smart enforcement priorities" to exercise "prosecutorial discretion" in order to best use his agency's limited resources. Johnson establishes three enforcement priority levels to guide DHS officers as they decide whether to stop, hold, or prosecute an illegal immigrant.

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Priority One is the "highest priority to which enforcement resources should be directed," the memo says. The category includes "aliens engaged in or suspected of terrorism or espionage, or who otherwise pose a danger to national security." It also includes "aliens apprehended at the border or ports of entry while attempting to unlawfully enter the United States." In addition, any illegal immigrant convicted of an offense involving a criminal street gang, or convicted of a felony -- provided that immigration status was not an "essential element" of the charge -- is targeted. Finally, any illegal immigrant convicted of an aggravated felony is included in Priority One.

The guidelines say Priority One aliens "must be prioritized" for deportation unless they qualify for asylum or unless there are "compelling and exceptional" factors that indicate the alien is not a threat.

Priority Two offenders, whose cases are less urgent than criminals in Priority One, include the following:

aliens convicted of a "significant misdemeanor," which for these purposes is an offense of domestic violence; sexual abuse or exploitation; burglary; unlawful possession or use of a firearm; drug distribution or trafficking; or driving under the influence; or if not an offense listed above, one for which the individual was sentenced to time in custody of 90 days or more (the sentence must involve time to be served in custody, and does not include a suspended sentence)

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DHS further defines a "significant misdemeanor" as an offense for which the maximum term of imprisonment is one year or less, but greater than five days. In addition, the guidelines contain a possible out for illegal immigrants accused of domestic abuse. "Careful consideration should be given to whether the convicted alien was also the victim of domestic violence," the guidelines say. "If so, this should be a mitigating factor."

Priority Two also includes "aliens convicted of three or more misdemeanor offenses, other than minor traffic offenses or state or local offenses for which an essential element was the alien's immigration status." But there's an important footnote to that. The three offenses must arise out of three separate incidents. If an illegal immigrant committed a single act that resulted in multiple misdemeanor charges, it would count as one charge for DHS counting purposes.

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The guidelines say Priority Two aliens "should" be removed — not "must," as with Priority One — unless they qualify for asylum or there are "factors" indicating the alien is not a threat. It's a significantly lower standard than Priority One.

Finally, Priority Three includes those who have simply violated the nation's immigration laws seriously enough to have been issued a final order of removal. The DHS memo describes them as the "lowest priority for apprehension and removal." They can be allowed to stay not only if they qualify for asylum but also if, "in the judgment of an immigration officer, the alien is not a threat to the integrity of the immigration system or there are factors suggesting the alien should not be an enforcement priority." In practice, that could prove a remarkably lenient standard.

So there they are: the rules that will guide implementation of President Obama's new "prosecutorial discretion" policy. Illegal immigrants who are also terrorists are clearly a top priority, as they should be. Illegal immigrants who are drunk drivers, sex abusers, drug dealers, and gun offenders — not so much. In addition, an illegal immigrant can run up a significant number of misdemeanor convictions — not arrests, not charges, but convictions — and still fall short qualifying for deportation. The president's new policies will likely make a number of illegal immigrants who are also criminals very happy.