Yes. Reselling genuine, lawfully purchased goods is protected by the first-sale doctrine in US law, and describing them accurately as pre-owned lululemon is permitted. What is not allowed is selling counterfeits or implying you are an authorized lululemon retailer.
ThriftUp is an independent reseller and is not affiliated with lululemon athletica. We never use lululemon's logo, photography or marketing in a way that implies endorsement, and we recommend buyers do the same: describe items truthfully, use your own photos, and never claim to be an official outlet.