While my Norinco works fine with a 20 round removable Tapco, I'd still want one with the original 10 round mag, preferably a numbers matching one. I still have the original.
Laws change, and one possibility is a ban on semi-auto rifles with removable mags. The SKS has no evil "assault rifle" features, and would pass with an original mag.
While in NY I had an email from the Dept. of Environmental Conservation, the game wardens, telling me it was OK to hunt with an SKS with original mag as long as there was a wooden block in there preventing loading of more than 5 rounds. So there's that, too.
To answer your original question, not sure if you mean a removable Tapco, or one of the 20 round fixed Chinese star mags. If the removable mag locks solidly in position, as mine does, it should be OK, but all guns are different and only a range session will tell for sure. The 20 round fixed mags, don't know how they work, but again, only a range session will tell.
I have one of the star mags, but have never tried it.
Good luck in your search!