There's a law from 1992 that describes the process of "state of emergency" and decrees
https://www.gazzettaufficiale.it/eli/id/1992/03/17/092G0253/...
Starting from article 5. It seems that any such state of emergency can last up to 12 months and be extended for 12 more months. The current state of emergency is going to last until the end of July, and there are discussions about extending it.
That's a regular law, not part of the constitution, article 77 of the constitution provides further rules:
https://www.senato.it/1025?sezione=127&articolo_numero_artic...
It's not clear, and I'm not a constitutional lawyer, but I found some interesting articles that describe the situation:
https://www.agensir.it/italia/2020/05/07/dpcm-e-coinvolgimen...
Context: the emergency acts are "decreto legge" and "dpcm" they are listed here:
http://www.governo.it/it/coronavirus-normativa
And this explains what dpcm are:
https://it.m.wikipedia.org/wiki/Decreto_ministeriale_(ordina...
Apparently, article 77 describes 2 deadlines: 5 days for the parliament to vote on the decrees and 60 days for the laws to be finalized.
I think that the crux of the issue is: whatever is inside those "decreto legge/dpcm", it has to be approved by parliament... There have been multiple such decrees, and the only controversial point is for how long can a parliament decision be delayed (in theory only for up to 5 days, but I'm starting to get lost in details).
Due to how many decrees have been created, I'd need to check for when each one of them has been (or is being planned to be) voted on