You can as an individual. And people do that, it's sometimes refered to as alcotourism, when you cross the border to buy cheaper alcohol in the neighbouring country. Finns go to Estonia. Estonians go to Latvia.
But as a company, you can't just import cigarettes or alcohol from another country and sell them at home. Cigarettes and alcohol have specific tax stamps on their packaging that make them restricted for sale in a specific country. People still do that, but at that point it's the black market.
Absolutely - it's also worth saying that there is a sophisticated tracking system to trace the manufacture of cigarettes from where they were created to the point in which they are sold (and all intermediary stops) in order to ensure that the correct tax is levied (despite there being no physical borders). This means that you can scan an individual cigarette box and see where it was manufactured, what tax was paid on it and every point it has travelled through in terms of the distribution chain.
This isn't fully implemented yet, but will be within the next few years.
