Poder não pode
This one is a bit tricky to explain. One translation could be “can, cannot”, or “that is not permitted/allowed, but…”
The “poder” in the expression is from the verb normally translated as “to can”, but in this case the meaning is “to permit”.
It is used to describe a situation where something is not permitted or not allowed. But regardless, people still do it anyway.
- Eu achei que não podia ir no mercado sem máscara?!
- É. Poder não pode né.