Immigration/travel law could encompass almost all the planets and signs in one way or another - as, indeed, does life. Saturn, Jupiter and Sagittarius are probably the most involved in present problems. Saturn the restrictor; Sagitarrius and it's ruling planet Jupiter relate to long-distance travel, with also some secondary connection to law.
See "Astrological Law and Order" - at the Starcats site, where there's a comprehensive rundown of how mundane astrology connects to various strands of law.
"Saturn creates the necessary order, structure, form and functions to mitigate the chaotic factors inherent in the negotiations of group enterprises. Saturn is associated with institutions representing the legal system, civil service, and all restraining/restricting forces in society. Saturn is rules, procedures, and guidelines. Saturn is associated with the administration of justice and has its affilations with police (law enforcement) and also the regimentation of military life and discipline. The attitude of a nation toward law, order, taboos, old practices, the old guard in politics, etc., are also associated with Saturn."
Restrictive Saturn's transit through Sagittarius, while linking to Jupiter and to Uranus does paint a correlating astrological picture of what we're watching happen: unexpected and excessive restrictions on some international travel. The opposition from Uranus to Jupiter initiates the problem, while softer aspects of sextiles and trines could be seen as relating to attempts to assist affected travellers by lifting the initial ban, using available legal means.