Dwight Lee writes,

The suggested policy is straightforward. Simply give Americans the right to sell their citizenships to non-Americans, with the sellers having to leave the country and the buyers allowed to move in with all the rights and opportunities of any other U.S. citizen.

Lee suggests that the very poor would be the ones who sell their citizenship rights. However, this may not be the case. The people who would sell citizenship rights would be people who get the least value for those rights at the margin. This might be someone who is getting ready to marry someone from another country or to retire to another country.

UPDATE: “PGL” recasts Lee’s argument in tariff-vs.-quota terms.

Putting price tags on human beings [might] sound objectionable to some, but some economists find the restrictions of the mobility of people even more objectionable.