If it is per gas station they could hypothetically require gas stations to individually keep track of licence plates and how much they fueled up in their own bookkeeping. See the same licence plate twice in a day? They don’t get to fuel up.
That way they could also enforce the rules by randomly checking ledgers
Edit: As for the fuel tourism, I’m not sure if banning the transport of fuel is enforceable. The EU has free movement of goods and people, so it is perfectly allowed to buy your petrol across the border.
As a historical parallel, back in 1973 the Dutch government rationed the sale of petrol by distributing fuel stamps. The consequence was that in the border regions people just went to fuel up in Germany where the petrol was not rationed.
If it is per gas station they could hypothetically require gas stations to individually keep track of licence plates and how much they fueled up in their own bookkeeping. See the same licence plate twice in a day? They don’t get to fuel up.
That way they could also enforce the rules by randomly checking ledgers
Edit: As for the fuel tourism, I’m not sure if banning the transport of fuel is enforceable. The EU has free movement of goods and people, so it is perfectly allowed to buy your petrol across the border.
As a historical parallel, back in 1973 the Dutch government rationed the sale of petrol by distributing fuel stamps. The consequence was that in the border regions people just went to fuel up in Germany where the petrol was not rationed.