For dealings within Russia, or through Russia, both companies and visitors don't have to cross any border, except the inter-regional "border"
You don't understand.. That companies will pay fines to Ukraine for acting like that. At the very least doing business both in Crimea and unoccupied Ukraine will be very problematic.
Same for for tourists, Even Russian tourists. Yes, we can't hope for extradition form Russia but should that tourist enter Ukraine later we have full right to arrest him for breaking our laws.
Legally, any businesses operating in Crimea were freed from responsibility after Crimea declared its independence
By international and Ukrainian laws that declaration of independence is illegal and has no power. Many, many countries said that.
By that logic, you could right now sue every business still operating in Crimea, and every person still living there.
In fact yes. That is likely will not be done for essential services. Exactly for the same reasons why we keep suppling electricity.
And yes, technically, each and every person in Crimea is breaking many Ukrainian laws following directives of illegal government. But as many of them are forced to do that we can't announce that they all are criminals
Likewise, anyone traveling into Crimea from Russia is not crossing international borders, according to Russian law, and unless there is a Ukrainian customs checkpoint on entry, the person never legally enters the territory of Ukraine.
Yes. The person never legally enters the territory of Ukraine. He enters illegally. As I said earlier Ukraine has little to no options to get this criminals out from Russia or occupied Crimea... But that doesn't change the fact that Ukraine has a right to arrest them