33.  Under this system, 8 U.S.C. § 1151(a) sets forth four different categories of  individuals who may be issued immigrant visas and the individual numeric annual limitations for  each category; § 1151(b) sets forth specific categories of individuals not subject to the numerical  limitation; and § 1152 sets a cap on the maximum number of immigrant visas that can be issued  to the nationals of any given country each year.   35.  Under 8 U.S.C. § 1152, the per-country limit for preference immigrants is set at 7  percent of the total annual family-sponsored and employment-based preference limits. This limit  means that no single country can receive more than 7 percent of the total green cards issued in a  year (unless they would otherwise go unused).   36.  Within the INA’s visa allocation system, qualifying family members or employers  are allowed to “sponsor” a noncitizen (the “beneficiary”) and any “derivatives”—i.e., the  noncitizen beneficiary’s spouse and unmarried minor children under the age of 21—for an  immigrant visa. To do so, a family member or employer must file either a Form I-130, Petition  for Alien Relative, or Form I-140, Petition for Alien Worker, with U.S. Citizenship and  Immigration Services (“USCIS”) on behalf of the “beneficiary.” This form establishes the  necessary family or employer-employee relationship to qualify for an immigrant visa.    38.  Demand for immigrant visas regularly exceeds supply. Scialabba v. Cuellar de  Osorio, 573 U.S. 41, 48 (2014). “As a consequence, the principal beneficiary of an approved  petition is placed in a queue with others in her category (F1, F2A, or what have you) in order of  ‘priority date’—that is, the date a petition was filed with USCIS.”  Id. (citing 8 U.S.C.  § 1153(e)(1); 8 C.F.R. § 204.1(b); 22 C.F.R. § 42.53(a) (2013)). Section 1153(e) thus provides  that family-sponsored and employment-based preference visas “shall” be issued to eligible  immigrants in the order in which a petition on behalf of each has been filed—that is, according to  the “priority date” of the underlying visa petition.   39.  The queues for each preference category are critical because a family member or  prospective employee abroad cannot apply for lawful permanent residence until a visa is  immediately available, or when the visa petition’s priority date becomes “current.” The  Department of State issues a monthly Visa Bulletin organized according to country of origin and  visa preference category.5 If there are sufficient visas available for applicants from a specific  country and of a specific preference category, then the Visa Bulletin lists that combination as  “current,” and all applicants matching that combination may file an application and receive the  visa regardless of their priority date. Similarly, the Visa Bulletin will provide final action dates  for oversubscribed categories that allow those with priority dates on or before the provided date  to finalize their visa applications and pursue their immigrant visas.    41.  Among family-based immigrants, Congress has prioritized the admission of  “immediate relatives”—i.e., the parents, spouses, and minor unmarried children of United States  citizens, because Congress did not place a numeric cap on the issuance of immigrant visas for  immediate relatives. 8 U.S.C. § 1151(b). This means that there is no “queue” for such family  members, and their petition’s “priority date” is of no consequence to when their visa may issue.   42.  By contrast to an “immediate relative,” other family members are placed in  preference categories that are tiered according to the family member’s relationship with the  petitioning family member. 8 U.S.C. §§ 1153(a)(1)-(4); see Cuellar de Osorio, 573 U.S. at 46–  48. The family-based immigration preference classes set by Congress, along with the applicable  visa allocations, are:  Preference  Number of Visas Allocated  Eligible Individuals  First (“F1”)  23,400, plus any numbers not  required for the fourth preference  Unmarried Sons and Daughters  (21 years old or older) of U.S.  Citizens  Second   STATUTORY BACKGROUND  