In Germany there already is a law called "Hacker(tools)paragraf" (§ 202c StGB).
It roughly states, that if you provide, create, sell, or distribute tools, which can / will be used to commit / prepare a computer related crime, shall be punished with one year in prison or a fine.
The problem with this is the vague wording: If dual-use tools like nmap are affected is open to discussion.
Maybe someone else finds a better translation; you can find the original text here: