A young mother in Alabama, 19, was driving down the street with her infant son when local police stopped her for failure to turn on her headlights. The officers discovered she had no driver's license and she was taken to the station.

That was on a Monday. Her son, a U.S. citizen, was turned over to the Department of Human Resources and, hours later, was reunited with his father, also a U.S. citizen. But Martha, the mother and wife of U.S. citizens, is an undocumented immigrant from Mexico who has lived in the U.S. since she was brought here at age 12. She was kept in jail and away from her family until Thursday.

This is partly due to Alabama's new "papers please" immigration law that requires local law enforcement to hold those suspected of illegal immigration, but it could have happened in almost any town in the U.S. that routinely calls immigration authorities when they suspect someone is here illegally. The local police would probably have let Martha go after paying her fine because she has no criminal record whatsoever, but when contacted, Immigration and Customs Enforcement (ICE), a federal agency, asked the local police to hold her until they could check her out.

Local clergy and advocates alerted me because Martha's case is precisely the type of case that President Obama's policy of exercising "prosecutorial discretion" under existing immigration law is designed to clear up. Those with no criminal record, deep ties to the community through family or their length of time in the community, are supposed to be the lowest priority under our record-setting deportation program that is designed to target serious criminals for identification and removal. I fought hard, side by side with advocates and clergy across the country, to push the Obama Administration to adopt a policy to not deport low priorities so that our limited resources are used on high value criminal immigrants.

Now, with states like Alabama, South Carolina, Georgia, Arizona and others passing laws to put more of their immigrant residents into deportation proceedings, this policy at the federal level to prioritize real criminals ahead of parents, students and working men and women, is all the more important.

So how did the policy work in this case? I happened to have participated in a meeting that Thursday between the Congressional Hispanic Caucus and Homeland Security Secretary Janet Napolitano. We were scheduled to get an update on the deportation prioritization plan and other immigration issues, but I used the opportunity to ask the Secretary why Martha was still detained after three nights in jail.

Eventually, later that day, in fact, ICE officers came to pick Martha up, ran the appropriate background check on her and then placed her in deportation proceedings with a date to report to ICE authorities one month later. She was released without bail late Thursday, having been in jail since Monday.

But why place her in deportation proceedings at all? She is an asset to her community and certainly an asset to her husband and infant child -- both U.S. citizens. Deporting her with or without her family makes no sense and is not in our national interest. And, given that we have reached our maximum system capacity for annual deportations at about 400,000 people a year, using one of our deportation slots on Martha and not a serious criminal makes no sense, either.

Late the next day, Friday, I received a call from an ICE official in Washington telling me that the deportation case against Martha had been dropped. No court date, no reporting to ICE for a supervisory visit in a month, just cancelation of the deportation case.

If you ask me, that is how our deportation policy should work. Although it took the better part of a week -- and a conversation between the Secretary of Homeland Security and a persistent member of Congress -- in the end, mother, child, and husband were back about their peaceful, productive lives as they should have been.

If you ask Republicans, however, a great injustice had occurred because a deportable immigrant was not deported. They have been badgering Homeland Security and ICE over the President's policy for months. Republican Senators and Representatives have pushed the "HALT" Act (H.R. 2487/S. 1380), legislation to take all discretion away from the President and his administration until a new President is elected. And they have threatened a contempt of Congress hearing against the Secretary for not turning over the name of every immigrant like Martha who was passed over for deportation in order to deport bigger fish and serious threats.

Note that Republicans have not used their time to explore ways in which: A) Martha (or immigrants like her) could come here legally in the first place; B) immigrants in Martha's situation could earn legal status; or C) how Martha could apply for legal status by virtue of her husband's citizenship without incurring a mandatory exile from the U.S. of 10 years. Doing any or all of those things would help solve the problem, not stir up political controversy over illegal immigration to weaken the President, which is, first and foremost, the goal of most House Republicans.

I am proud to live in a country where the rule of law and federal immigration preeminence enshrined in the constitution are tools to undo what legislatures in Alabama, South Carolina, and elsewhere have tried to do when politicizing and polarizing the immigration issue. When the Supreme Court takes up the Arizona "papers please" law, SB 1070, the conflict between federal priorities to remove serious criminals and state policies to deport as many people as they can catch will be a central issue. And clearly the constitution says that federal policy should prevail. A federal judge enjoined the implementation of most of South Carolina's "papers please" law, scheduled to take effect January 1, precisely on this basis.

I am also proud of President Obama, Secretary Napolitano, and ICE Director Morton for rolling out and defending the deportation prioritization policy. Despite subpoenas, legislation and flamboyantly fact-free rhetoric from Republicans, the president is right to make this adjustment to our deportation policy until such time as we have immigration laws that are in our national interest and are, in fact, enforceable.

Of course, I think the new policy should be applied more aggressively and uniformly so that immigrant mothers like Martha don't needlessly spend three nights in jail so that fewer immigrants' lives are disrupted.

I also think there are a number of other things the president and his administration can and should do under current law, including making it possible for spouses like Martha to apply for legal status through her U.S. citizen husband without facing a 10 year mandatory exile in another country. The policy that eventually reunited Martha with her family in this case should not require several days in jail or the attention of a U.S. Congressman or a Cabinet Secretary to be followed, either. And, based on formal research and an informal tally of calls coming to my office, it is by no means clear that everyone in circumstances similar to Martha's is receiving the appropriate oversight and discretion of immigration authorities.

But I learned a lot from Martha's case -- and from the cases of Gabino and his two U.S. citizen kids in South Carolina, Janina and her citizen husband and son in Chicago, Serge and his citizen wife and kids in West Virginia and countless others -- and that is that the government works if you make it work.

Every day you have to be an activist to ensure that the government is being fair and equitable with people. Schools, bus terminals and lunch counters in Alabama, Georgia, and South Carolina did not desegregate themselves. Wars do not end until people take action to end them. Wall Streeters will not put national interest over personal gain on their own. And while the arc of the moral universe is long and it does indeed bend towards justice, as Dr. King taught us, most times, people of conscience have to expend considerable energy to assist in the bending.