Multi-speed integration is a scenario where existing member states integrate at different paces, where certain member states opt into greater integration in specific policy areas, while others opt out. This would not apply retroactively, so existing policies would remain unified, but new policies would be differentially adopted.
In the African Union, salient policy issues include a common currency, common market, free movement of people, tariff harmonization, and a defence pact/consensual peacekeeping forces.