Careful - don't mix up two separate issues
1 - compliance. As any company, Google has to comply with local law, which raises interesting questions in itself about jurisdiction - Google Switzerland, for instance, has a problem as that is responsible for the whole EU but Swiss laws differ. So, for email security you'd like to hold it in a country that is fanatic about Data Protection and will require *evidence* or warrented suspicion before a warrant is issued (I would not call the UK RIPA 2000 a barrier to unauthorised snooping).
2 - custodial duties. Once a warrant has been issued, the question is what happens to the data released. You will find in most countries that there is are no real custodial duties imposed, so if you're a private banker or a GP you may find that your precious data is suddenly handled by a junior policeman. The joys of yelling "terrorist". There are, however, countries where data released under warrant is strictly controlled. In Switzerland, for instance, will you have an investigative judge, who is the only one to look at the released data. Only on evidence of crime can the exact data set that proves this be released for evidence.
I would not touch Gmail even if it was a Gstring, sorry. But I'm picky that way anyway, I intensely dislike people spying on me for dishonest reasons (I'm OK with proper due process, because I don't have anything to hide - I just hate abuse).
Oh, and I put my money where my mouth is - I just set up a new email system in Switzerland. Just have to write up the details..