Yes. It is only for legality reasons. It is my understanding that you can modify a magazine any way you like, as long as it still functions in the original gun. If it were not to function in the origional firearm it was designed for, them you would have constructed a new high cap mag. And obviously unless you are LE/military, you (or I) cannot be in posession of a post ban, high cap mag.
This is all for our own saftey of course. Cough, cought, bullshit, bullshit.