Some backgroud :
A bootloader is a very low level piece of software that runs first and loads an operating system of some other tool. On a lot of new Android devices the bootloader is "locked", that means that it checks if the digital signature of the installed OS and then only accepts to boot the device. Some phone manufacturers have started to lock bootloaders in order to prevent any system modification whether it is done by a legitimate user or not.
My question :
Android is an operating system based on Linux, and Linux is distributed under the GNU GPL v2 license. The GPL v2 grants some rights to the user, in particular being able to modify a program licensed under it.
As bootloader locks prevent users from modifying an Android phone's software in some ways, is it legal for phones manufacturers to prevent the user from removing the bootloader lock ?