Surely not if there are properly described as such so that the buyer is in no doubt about what they are buying? The issue (if any exists) is one of intention. If you intend to sell a Squier with a Fender decal on it as a Fender, then that is clearly wrong. To sell a Squier with a Fender decal on it described as 'a Squier with a Fender decal on it' is not, and many such Squiers (and bitzas) have been sold on this site without issue.
In any case, the Fender/Squier thing is like the baked-bean situation. Many Squiers I've played have been at least as good, if not better than, many Mex and even US Fenders I've played, so it really just becomes a branding and marketing issue...