They can certainly be arrested and extradited to the US if they were to travel outside of Russia.
That aside. The indictments explain the extent to which Russia was committed to their efforts here. IMO, that is more imortant.
Mueller knows his chances are between slim and none that any of those Russians will travel to where they can extradited to the USA. But that wasn't his point. Mueller had to prove his investigation wasn't a witch hunt by showing there were underlying crimes he was investigating. Since collusion isn't a crime, he showed conspiracy to commit identity theft, and conspiracy to commit wire fraud serves to justify the investigations underlying crime requirement.
Mueller has many other indictments up his sleeve. How do I know? Mueller hasn't leaked any of his moves in advance, and has repeatedly taken everybody by surprise, with each indictment or guilty plea providing another piece of the Russian puzzle.
Mueller is playing three dimensional chess while Donald and his pals are sitting on a floor in the Romper Room floor engaging in a zesty game of Hungry Hippo.
And with his Magic Mirror, Bob sees Michael and Don Junior and Paul and George and Jared and Russian Trolls and and oh look - there's Donald J Dotard himself!
Clapper says there are more shoes to drop No wonder trumps tweets bash FBI in school shooting
Why would you believe a proven liar like Clapper?
It's obvious that some one DEEP into the Russian investigation is helping Muelleur.......and the only proven liar I know of is Trump