Loosing 2 passports at the same time
So, most countries are part of that convention according to which you can’t make your citizen stateless
Now, let’s take a dual citizen
Let’s say French and British (both part of that convention)
The said citizen could lose French citizenship, after what Britain would not be able to do the same, otherwise the person would be stateless
Now, what happens if both countries strip the citizen of his citizenship at the same time, at the same date of the decree/decision, with the decrees entering into force at the same time ?