That's a silly statement. I can't legally disable the emissions controls on my car nor can I legally modify my router to use banned spectrum bands, but that doesn't mean i don't own both things.
Of course you can. You can legally disable whatever you want on your vehicle. What you won't be allowed to do is have it pass inspection, or drive it on public roads.
And as the other poster mentioned, (and I actually do have an amateur license,) I can modify my router to transmit on any band that I have privileges on, that allows that particular emission type, (60-meters/5MHz is the only one I can think of that would completely bar something like that.) For that matter, I could modify it to transmit on bands where I don't have privileges, and you could, too. What neither of us would be allowed to do is transmit on publicly owned airwaves not allocated to that use.
In both cases, it's not that you can't modify your own equipment, (car, wifi router,) it's that you cannot use uncertified equipment on a public owned resource, (public roadways, public airwaves.)