It's a reference to the statute defining inadmissible aliens:
Quote Quoting 8 USC 1182(a)(3); INA 212(a)(3)
(a) Classes of aliens ineligible for visas or admission

Except as otherwise provided in this chapter, aliens who are inadmissible under the following paragraphs are ineligible to receive visas and ineligible to be admitted to the United States:
(3) Security and related grounds
(A) In general

Any alien who a consular officer or the Attorney General knows, or has reasonable ground to believe, seeks to enter the United States to engage solely, principally, or incidentally in
(i) any activity
(I) to violate any law of the United States relating to espionage or sabotage or

(II) to violate or evade any law prohibiting the export from the United States of goods, technology, or sensitive information,
(ii) any other unlawful activity, or

(iii) any activity a purpose of which is the opposition to, or the control or overthrow of, the Government of the United States by force, violence, or other unlawful means,