Jeff Watson has some great videos on the do and dont's of legally wholesaling in Ohio. See
http://watsoninvested.com/wholesaling/
(I'm not an attorney so the following are just my opinions and interpretations)
Wholesaling (assignments and back to back closings) is legal in Ohio. I am not sure if Ohio is "technically" more restrictive that any other state. The "no nos" in the video probably shouldn't be done in any state. I think Ohio has probably started to ENFORCE their laws and guidelines more than any other state when it comes to people trying circumvent being a licensed real estate agent.
The main problem it seems is about how one may market their wholesale deals and their intent when entering into an agreement with a seller. The 3 biggest takeaways I got of the videos were
1) You can't have weasel clauses saying the contract is contingent on finding another buyer.
2) You can't market house you don't own and/or lead people to believe you own the property. For example put a photo of the house with the address and saying the house is for sale. Technically this would include not only wholesalers who assign contracts but also rehabbers who buy properties outright as well. According to that interpretation a rehabber can't advertise a house they have not bought yet even though they plan to invest thousands of dollars of their own money to buy and renovate the house. (I doubt a rehabber with a track record of buying and renovate houses would get in trouble)
3) What you can do is market your contract and equitable interest in the property WITHOUT the full address and photos. For example instead of "I have a house at 123 Main Street for sale" you would say "I have a wholesale deal under contract for a house in the <example> neighborhood on Main Street"
The broad generic concept of Wholesaling itself isn't illegal. It is the unscrupulous and misleading marketing and contractual tactics of some people that is what is illegal.