The term legal is subjective prior to charges, as it's on the opinion of the lawyers based on past cases.
By offering Zelle banking and Paypal, they become subject to US law, as Zelle only serves US residents. From my understanding of US law, one can't operate an exchange to facilitate money transmission, if they have custody and control. Uniswap got off their court case, by demonstrating non-control through an algorithm that acted autonomously. Because Reto isn't working off autonomous smart contracts, and because they offer Monero to Zelle (where the end-product is clearly US dollars without KYC), I believe IF a court were to rule on this, then it very likely would be considered a violation of current money transmission laws. And to clarify, I believe Bisq is illegal also.
On the other hand, XMRBazaar very clearly is legal, because the end-product isn't money itself, it's random products that are owned prior to the buyer giving XMR, and the funds can go directly to the seller's wallet. Further by being hosted in Iceland, it's not even clear what law applies to XMRBazaar for digital services.
nostr:npub1ge0tzdqy6useekgu9d9g5l3s3t2wpx7p9xxuprz7ajzjaxl4mgyssejcs3 nostr:npub1arhp6h8w2mc2jnrfrzt6fl92tasx5m5qtmw7837ffhs887fuqwfq92zhzj nostr:npub1ah3aj4mhfew4c7txfdd4paf3wr5syntkeyxenl9fxf9rejte2wpqwcl76e