Well well well... If you forgive the terrible english from a frenchie (excuse my french

) , here is my answer regarding the source of the 180 days limit for turists.
I think it's a kind of doctrinal problem, the law actually dealing with migration not being that well written in some aspects.
The ultimate ley de migraciones (25.871) shows an obvious contradiction, I am referring to articles 122 and 124.
It's a doctrinal aspect, it means that people interpreting the law need to imagine what the legislator meant.
Article 122 leads to think that the new law wipes out all the effects of the previous law and reglementary
decretos or decisions while Article 124 tells us that (
dispose en french, I don't know the castellano equivalent for it) previous laws and reglamientos will still be in effect until the new law (and very likely this means the new reglamientos as well) come into effect.
If I put it simply, the new law wipes out the previous law unless certain aspects are not defined after the new law is passed (sounds weird, messy but the text is messy itself, not me. I'm just trying to understand).
Therefore the previous decretos (previous to the new law) are still in effect until a new decreto changes the rules.
Therefore (bis repetita) : the decreto referring to the old law (decreto 1023/94) still applies since a new one was never passed.
And this works too for all the reglementations that were passed before this new law 25.871 was passed.
This is why no certain answer can be found over the net : the law 25.871, especially in its article 122 and 124 is written in a very weird way. Old norms still apply until new ones are taken.
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On a side note, since this is a foreign expat forum (many different backgrounds/opinions), if some could make an effort not to fall into personal fights, I am quite sure this would be quite beneficial for all of us.
Cheers