All air and sea ports have been put on alert for missing 14-year-old girl and 35-year-old John Bush.
Police say sightings suggest they are heading south from Yorkshire and that any move to leave the country would be "very foolish".
More top news
The US president’s words earned a scathing riposte from the country’s leader.
California Attorney General Xavier Becerra said the suit says the action violates the US Constitution.
Police are searching for Hugo Palmer and his friend Erwan Ferrieux.