In a clause is contrary to public policy, it may be unenforceable in that jurisdiction and thus they could use the code without violating the license. The unenforceable clause will be skipped over by the courts. It is a nullity.
IANAL, but GPLv3 requires software to be modifiable by an user.
> If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information.
However, it can be still followed by not letting even Wi-Fi router vendor update the firmware on a device.
> But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).
Otherwise, you cannot provide the program at all. It's intentional, it's supposed to provide pressure on regulations like FCC regulations, at least in theory (vendors who already use GPLv3 software, could complain to FCC that they cannot use free software licensed under GPLv3).
> If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all.
No, they couldn't. The GPL is a grany of rights, not a restriction of them - if you can't fulfil the criteria then you do not get the grant, regardless of public policy.
