Ableza
Headphoneus Supremus
If a manufacturer states "if you open the case the warranty is void" then that is the policy. The distinction is if it is clearly published as a restriction. "No User Serviceable Parts" is in the same category. But yes, it is the manufacturer's burden to prove that tampering occurred if they wish to viod a warranty on a particular product, but that is far easier than you might think. My company honors warranties for two years from date of MANUFACTURE no matter how badly some idiot user has damaged it, in all but the most obvious cases. It's generally cheaper to do that than to fight it. But trust me, when I was the compliance and IP officer I went out of my way to void warranties for people who were obviously trying to run a game and get us to pay for their screw ups.