“Would it be possible for someone who has a U.S. citizen relative living in Ireland to be sponsored for a green card? A friend of mine who was born in Ireland has a U.S. citizen brother who lived here for many years, became a citizen and moved back to Ireland. My friend wants to come here and was wondering if her brother’s citizenship would be of any use to her for sponsorship purposes.”

No, it really wouldn’t, for a couple of reasons. First off, U.S. citizens can sponsor siblings for permanent residence under the family preference Fourth Category, which allocates 65,000 green cards on an annual basis.

However, the category is hopelessly over-subscribed, which means that demand is far greater than supply. For March of 2010, those who filed applications on or before November of 2000 are being called for final processing, making the wait for a sibling-based green card a minimum of 10 years, and likely much longer.

Equally as important, virtually all permanent resident applications must be accompanied by an affidavit of support, signed by the visa sponsor. The affidavit, as we discussed in last week’s column, guarantees that the sponsor will assume financial responsibility if the permanent resident becomes a public charge.

The person who signs the affidavit –- with regards to your question, your friend’s brother -– must be domiciled in the U.S. This is a non-negotiable that, from the information provided in your letter, would render the brother ineligible to complete the affidavit, and therefore unable to act as visa sponsor for your friend.

How does the State Department define domicile? “To qualify as a sponsor, a petitioner who is residing abroad must have a principal residence in the U.S. and intend to maintain that residence for the foreseeable future,” according to www.travel.state.gov.

Provisions are in place for U.S. citizens who are residing outside of the country on a temporary basis, mainly for work or family reasons. Also, those working abroad for the U.S. government are considered to be domiciled in the U.S.

“Temporary may cover an extended period of residence abroad. The sponsor living abroad must establish the following in order to be considered domiciled in the United States -- he/she left the United States for a limited and not indefinite period of time; he/she intended to maintain a domicile in the U.S.; and he/she has evidence of continued ties to the U.S.,” the State Department says.

How can a citizen living abroad re-establish a U.S. domicile? Pretty much as you would think – obtaining a residence, getting a job and registering kids in school are three such ways. Showing evidence that a residence abroad has been surrendered is another.

The affidavit sponsor may, if necessary, enlist the assistance of an agreeable co-sponsor to meet the financial requirement, which requires the sponsor to show a household income equal to or higher than 125 percent of the U.S. poverty level for the household size. However, having a co-sponsor does not take away from the fact that the primary sponsor must be a U.S. resident.

Given these realities, your friend will have to pursue another route to come to the U.S.