John Christoforidis, of Garden City, New York, a stockbroker registered with Spartan Capital Securities LLC, has been barred from associating with any Financial Industry Regulatory Authority (FINRA) member in any capacity because Christoforidis refused to testify during a FINRA investigation. Letter of Acceptance, Waiver, and Consent No. 2018056490313 (August 7, 2024). FINRA’s action against Christoforidis…