How is it possible that after 15 years the supreme rabbinical court in Israel can invalidate a conversion? I thought that once a person did giyur they are a Jew & if they frei out it is just like a born Jew who freis out. IMHO this whole business is political rather than halachic in nature & will only serve to strengthen the heretical Conservative & Reform movements.

The Supreme rabbinical court did not invalidate a conversion. A lower level (local)court did so, and the Chief Rabbis invalidated that decision. In general, a conversion may not be undone. The claim in this case was that the beit din that performed the original conversion was not authorized. In my opinion there is certainly a political element to that claim, and that is the main reason that the decision was reversed. The entire fiasco did not raise the level of respect for halacha and the rabbinate in Israel. Fortunately, the chief rabbis understood this and have tried to undo or at least minimize the damage.