Even if Hallachically Jewish by birth, it means nothing for the Israeli Law of Return. In order to be accepted in Israel under the Law of Return, a person must be both Hallachically Jewish (birth or conversion) AND identify himself as a Jew without practising another religion, or be a child or grand-child of a Jew/Jewess by Hallacha even if he, himself, is Gentile and keeps another religion. Interestingly, under israeli Law, a Gentile of Jewish origin can be a citizen even if he practises another religion but, if he is Jewish himself, he is not accepted in case of having rejected Judaism.
It would be interesting to know what religion, if any, had this man up till now and if he gave it up when he supposedelly discovered that he is Jewish.
But if he goes with a tourist or student visa just to know and learn, no questions are asked. The media might harrass him with questions fro being famous, but he is a human being as any other and has every right to make his trip a private issue.