It's not the copyright law that is lax in these countries, but rather the level of monitoring and enforcement required by ISPs. For most ISPs they gain nothing by sending anti-piracy letters to customers in the absence of any particular law that mandates ISPs enforce anti-piracy. Instead they may find customers leave and go to a competitor. The most they do is the bare minimum required by Govt, usually blocking certain domains and only sending letters if a third party has done the hard work of identifying the IP address of a pirate. When studios sue ISPs they generally lose, or go for settlements (see BMG vs Cox). ISPs have spent a lot of time and money lobbying to be left out of piracy enforcement.

You could compare it to underage drinking, a bar's main incentive to not serve underage customers is to avoid large fines for doing so. If those fines didn't exist one might assume many bars would be more lax on checking ID. A bar might argue that if underage drinking is illegal then that's a matter between the drinker and the police, it's not the bar's job to spend money on security to check patron IDs. This is essentially what ISPs have argued.