Something voiding the warranty or being illegal is quite different matter though. I'm pretty sure that disassembling your phone voids your warranty but I would be surprised if it was illegal.
Disassembling your phone only voids the warranty on the overall device, not on the individual parts. Also changing the software does not void the warranty of the hardware.
Also if a contract contains a clause forbidding you to disassemble, decompile, or debug something, then the clause is automatically void.
Exactly. Doesn't matter what Motorola says. The Terms they made me "read" and "agree" upon are void because they go against the law. I'm free to get rid of the Motorola software on my phone and replace it without voiding the 24 months warranty on my phone.