A while ago i read that companies sometimes use SLS in conditioners as preservative (in fact if present, it is among the last positions of the INCI, so in small quantities).
Anyway i'd never buy such a condish
Often they put the 'No SLES' label on the shampoo bottles, but if you read the INCI name you can find another kind of sulfate (i.e. ammonium or coceth laureth sulfate).
Here in Italy it's difficult to find a 'No Sulfate' shampoo in the supermarkets, unless you check the newborn stuff shelf or the biological one