United States immigration is governed by the Immigration and Nationality Act (INA), administered by USCIS (within DHS), the Department of State (visa issuance abroad), the Department of Labor (PERM and prevailing wage), and CBP (port-of-entry inspection). Nonimmigrant visas (F-1, H-1B, J-1, L-1, O-1, B-1/B-2) authorise temporary stays for specific purposes. Immigrant visas lead to lawful permanent residence (the green card) via family, employment or diversity categories. Petition-based work routes require a US employer or self-petition (NIW, EB-1A).
The F-1 student visa is the most common Pakistani entry route. Issued for the length of study programme plus 60 days, F-1 includes Curricular Practical Training (CPT) during studies and Optional Practical Training (OPT) for 12 months after graduation. STEM-designated degree holders get an additional 24-month OPT extension — total 3 years of post-study work authorisation. From OPT, transition to H-1B specialty occupation requires an annual lottery (~85,000 visas allocated each fiscal year, ~25% selection odds), then 6 years of H-1B status if Labor Certification (PERM) and I-140 immigrant petition are filed for green card sponsorship.
Employment-based immigration runs five priority categories. EB-1 Extraordinary Ability for top professionals, EB-2 Advanced Degree (including the National Interest Waiver self-petition for exceptional contributors), EB-3 Skilled Worker. Per-country caps mean Pakistani EB-2 and EB-3 face multi-year backlogs (currently 2+ years for EB-2 Pakistan in the Visa Bulletin). Direct family sponsorship by US citizens or LPRs runs alongside. Naturalisation after 5 years of LPR (3 years if married to a US citizen), passing the civics test in English. Pakistan permits dual citizenship with the USA.