Normal size magazine registration is exactly what the EU Commission wanted after the last Paris terror attacks. When they found out that there are tens or hundreds of millions of them in EU, for example surplus AK mags used in Bulgaria to mix with macadam to pave roads, and the vast majority of them without any serial numbers or identifying marks, their solution was not to register them all, but still have them licensed.
And that's what we are getting soon, magazine licenses. You will soon need one to buy or sell normal capacity mags (more than 10 rounds for a rifle and more than 20 for a pistol). The similar ammunition license for possessing and acquiring hollow point ammo for example costs about $40. Per legal precedent, those with grandfathered magazines should get theirs free of charge though...