Comment by mytailorisrich

That's not actually the case, strictly speaking. Residence in another EU country requires meeting certain criteria even if some countries (like the UK when it was in the EU) do not check or really enforce them. This also means that an EU citizen can be deported from another EU country back to their home country if they don't meet those criteria.

"Permanent residence" is also again different and requires residence under those criteria for at least 5 years.