Washington (CNN) Attorney General William Barr has overruled an asylum decision that protected some immigrants seeking asylum based on family ties, the Justice Department announced Monday.

Thousands of people could potentially be affected by this ruling, according to the Catholic Legal Immigration Network, an advocacy group which represented the respondent as co-counsel.

The case, known as Matter L-E-A, is about the son of a man "who owned a store targeted by a local drug cartel." The second time the son, a Mexican citizen, illegally crossed the southern border in 2011, he sought asylum in immigration court.

Barr found that the previous ruling by the Board of Immigration Appeals had "improperly recognized" the father's immediate family as a "particular social group," in effect overturning precedent.

In order to be granted asylum, a migrant must establish that he or she is unable or unwilling to return to their origin country because they have "suffered past persecution or has a well-founded fear of future persecution on account of 'race, religion, nationality, membership in a particular social group, or political opinion,' " according to the ruling.

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