Can I kill him?

[Zion]

A russian took back his mine after being gone for a month, can I kill him while he's sleeping in a bed?

[Onionfighter]

The only way to kill someone offline is by using scents to summon them.

[Brackwell]

You could try luring him into a trap? Build a claimed area and make signposts blocking off an area he'd have to go through, so when he broke them he'd leave vandalism scents.

[ejonkou]

You shouldnt kill him. He found the mine first.
And 1 Month isnt really a long time either.

He'd be getting some buds for revenge or something if you would.