You don't have to be resident in the UK - there's a category for "expatriates" (does anyone really check stuff like that?) but you do have to be a British citizen.
BTW, do any of the government bods know that rappers etc aren't proper swords? Have to admit, I could think of a few reasons for having a cutting edge on them...
I've signed the petition, very quick & easy, but there's one of those emailed confirmation-links that drop into your Inbox, which you have to click on to validate. No problem, but be warned that the sender's name displays as 10 Downing Street. "Yeah, right" I thought when I saw it, and was about to dump it into the spam bin along with all the bank account warnings, Paypal suspensions, assorted medications, and fantastic prizes I won. But it's the real thing. So go sign, and you too can get your very own email from the prime minister's office.