The only issue I'd have is that the label serves to identify the ball and can be used to determine the legality of it. If the balls have the USBC* logo, there shouldn't be a problem. I know you can re-engrave logos and serial numbers if they are worn off.
You might want to fire off an e-mail to the USBC. I know you're not in the US, but they'd know what's what for USBC competition. Overseas organizations should have similar rules.
SH