THE CURRENT EXCHANGE DELISTING PROCESS. Issuers that wish to trade securities on a national securities exchange must register the securities for listing and trading with the exchange pursuant to Section 12(a) of the Exchange Act. Section 12(b) requires an issuer to register its security or a class of securities with the SEC by filing an application.[1] A security admitted for trading on a national stock exchange will be listed for trading so long as the issuer satisfies the exchange's initial listing requirements.
An issuer's security is withdrawn from listing and trading on an exchange for two primary reasons. First, a security may cease to be eligible for listing because the issuer has failed to meet the exchange's continuing listing requirements, which also includes the issuer's duty to file timely annual reports with the SEC. In this case, the exchange will initiate a proceeding to delist and deregister the issuer's security. Second, the issuer may wish to voluntarily remove its securities from listing on one exchange to either list and trade the security on another market, or to permanently cease trading in the security. *******
But I do not know why this would be trading if it is really de-registered. Confused.