If you have information especially links to English translations of gun laws in other countries please send them to me. (firstname.lastname@example.org) or make a comment to this post. I have found some information about insurance of 100,000 euros being required in Portugal. In Germany the amount is one million euros and the law (link to German Weapons Law) says:
Requirements for a licence
(1) In order to be granted a licence, applicants shall
1. be at least 18 years of age (Section 2 (1)),
2. have the necessary reliability (Section 5) and personal aptitude (Section 6),
3. demonstrate the necessary specialized knowledge (Section 7),
4. demonstrate a need (Section 8), and
5. enclose proof of liability insurance cover of one million euros for personal injury and property damage when applying for a weapons licence or shooting licence.