Yes, as a foreigner there is no such thing as a right to enter the USA - the CBP agents can refuse you entry for any reason whatsoever and you have no recourse (they could be breaking various laws of their own and face personal liability for their own actions, of course, such as if they were seeking a bribe from you - but that doesn't give you any right to sue over their refusal to admit you). The only exception is asylum seeking, where there is a legal right for your asylum case to be heard.