It is a matter of scope
To be "banned in" describes the jurisdiction to which a ban applies. To be "banned from" describes the zone(s) that the ban applies to within that jurisdiction.
In many cases, the scope is the entire jurisdiction:
A ban in Bob's Bar bans Joe from Bob's bar. Joe is banned from Bob's Bar and he is also banned in Bob's Bar, but your use of preposition determines if you are talking about Bob's Bar as the jurisdiction or Bob's Bar as the exclusion zone.
But sometimes it its not:
A ban in the United States bans Joe from entering any Bob's bar. Joe is banned from all Bob's Bars in the United States, but he is still allowed to be in and do other stuff in the United States even though the ban applies to the whole United States.
This also applies to less tangible things:
A ban in TicToc(*) bans Joe from TicToc. Joe is banned from TicToc and he is also banned in TicToc, but your use of preposition determines if you are talking about TicToc as the jurisdiction or TicToc as the exclusion zone.
A ban in the United States bans Joe from using TicToc. Joe is banned from using TicToc in the United States, but he is still allowed to be in and do other stuff the United States even though the ban applies to the whole United States.
There are also some weird cases where a ban zone extends outside of the jurisdiction (because some politicians are that cocky)
GDPR is a ban in the European Union that bans anyone from saving an EU citizen's PPI without encryption. So even an American is banned from saving an EU citizen's PPI without encryption, but GDPR is a ban that is only in the European Union.
(*) This would be an unusual thing to say, but still grammatically correct. A program or system can contain a ban in its code or rules. So you can be banned in a non-physcial jursidiction.