Pretty sure that 1 Star cards were allowed now. Old ELO did not allow it.
I remember a player 0_AAR had one of the top scores in EFC with a 1 Star Ginger in their deck.
In fairness, there are not many good 1 Star options out there, but you are welcome to use any.
1 Star cards are not banned if they are allowed in the zone and your deck makes a 25 Star deck without doubles.
The old format prohibited decks from having more than 1 5 Star card and any 1 star card.
In short: 1* Not banned in EFC. Likewise 2 5* not banned in EFC.
Hope this answers your question.