Basically, RBG is a digital rights management system. Issuance, burning, secondary issuance, reissuance etc - are different forms of rights managed by RGB, alongside asset ownership rights. How these rights are structured and managed is defined by particular RGB Schema. Rights are controlled by Bitcoin script in Bitcoin transaction output; i.e. whoever can spend the output, has/owns the right, which was assigned to that output. Assignments are done with the current right owner; i.e. in case of genesis, is the issuer.