Labradoodle Rescue & Goldendoodle Rescue
No, it's against the law in Oklahoma (and 25 other states) to sell a puppy before the age of 8 weeks. https://www.animallaw.info/topic/table-state-laws-concerning-minimu... However, I'm not sure about giving them away.
At any rate, I would flag the CL ad. You can also try messaging the owner, but that can sometimes provoke a hostile response.
5 weeks is way too young for any dog to leave its mother and litter. Puppies don't even develop bite inhibition until between 6-8 weeks.
It's heartbreaking, but unfortunately, all too common, especially in rural areas.