The Supreme Court's criteria for who can be barred from entering the United States under President Donald Trump's travel ban may confuse the U.S. officials overseas charged with implementing it and trigger a new round of lawsuits, experts said.

People with a "bona fide relationship with a person or entity" in the United States are spared from the temporary ban affecting people from six Muslim-majority countries and all refugees that the justices Monday allowed to go partially into effect.

"There's no precedent for something like this that I'm aware of," said Jeffrey Gorsky, a former legal adviser to the State Department's Visa Office, referring to the new "bona fide" standard.