If a package is removed (retired) from Fedora, for example because it was renamed, it needs to be blocked in Koji. This prevents creating new package builds and distribution of built RPMs. Packages are blocked in the listing of tags, due to inheritance it is enough to block packages at the oldest tag will make it unavailable also in upstream tags.

The blocking of retired packages is done by the block_retired.py script as part of the daily Rawhide and Branched composes.