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Your previous expert has opted out and I have opted in. On this website, I do not always get to give good news, and this is one of these times.
There is no right to enter the USA, even if one has a visa. The border authorities (CBP, ICE, USCIS, and others) have discretion on whether to allow someone in. So a person can be turned away by the authorities. Period.
In order to file a lawsuit, one would need a cause of action rooted in state common law actions or federal statutes. CBP's actions do not amount to illicit conduct under common law actions or federal statutes. The US government does not have to let anyone in. If CBP has reason to believe that a person may overstay their visa, have dual intent, or otherwise, then they may be denied entry.
Anyhow, he has an unlimited time to file the complaint - see HERE:
However, I doubt it would lead anywhere because CBP did not violate any laws. And he cannot file a lawsuit because - again - CBP did not violate any laws by refusing him entry because a foreign citizen cannot demand entry into USA. Even with a Visa Waiver Permit. A VWP simply states that the person does not have to petition the US Consulate/Embassy for a visa prior to flying to USA. However, they would still face the same discretionary entry decision whether with a VWP or on a B2 visa, for example.
All of this has been adjudicated and confirmed by case precedent in USA in cases such as Sabataityte v. Powell, Saavedra Bruno v. Albright, and Hermina Sague v. United States, amongst others.
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