Sjs, they could just put tags on the clothing in places where it’ll show when you where them. If the tags are cut, no returns.
Ames, when I was a teenager, I became excellent at removing obvious tags without ripping them (if I wanted to take tags off on Shabbos – I wasnt trying to return anything).
Its unfortunate that no matter what the system, people will try to take advantage (in a bad way).