In the wake of President Donald Trump's new border policies, European countries like the United Kingdom are updating their U.S. travel warnings.

The United Kingdom updated its advice for travel to the United States on Thursday, warning of harsh consequences for British passport holders who violate U.S. immigration laws. The notice comes just a day after Germany updated its travel advice after three of its citizens were detained trying to enter the U.

Two major European countries are warning citizens about travel to the U.S. following high-profile cases in which American federal immigration authorities detained tourists and U.S. green cardholders trying to enter the country.