For example, some smaller euro area countries actually regained sovereignty with the euro by regaining influence over monetary policy at a higher level. Something similar may hold for countries joining the EU, when they can participate in the shaping of the single market rules rather than having to adjust to them.
In a globalised economy, the dwindling of individual influence may actually be reversed through integration. Of course, this is only true if countries and their citizens are involved in joint decision-making. The degree of participation is therefore much more important than the level of policy assignment to determine whether sovereignty is lost, shared or actually gained.