I just stumbled upon this thread and wanted to put in my $0.02.
An assignment of contract is not illegal in the state of Oregon. I can speak on this personally because I've actually been investigated by the state of Oregon for unlicensed broker activity (and didn't face any legal repercussions). I know @Cody Cox very well, and also moderate the "Deal Analysis and Discussion" meeting for the NWREIA that Cody used to be the president of.
The most imperative words that @Ned Carey mentioned was "for another, or on behalf of another."
These words are crucial, because the entire legality of wholesaling (aka assignment of contract) hinges upon these words if you are unlicensed (like myself).
Assignments in general fall more under contract law than real estate law, because a wholesaler does not sell real estate. I technically don't sell contracts either. An assignment is a completely different story, because a willing buyer is willing to pay me a fee for the right to take my place as a buyer. I didn't sell my contract to them - they paid me (the buyer) a fee to take over my place as the buyer. There is no commission involved at all, so remove that language from your vocabulary.
Time and time again people say "Wholesaling is illegal," or they say "wholesaling is legal." After surviving investigations for unlicensed broker activity in the states of Oregon, Washington, and Colorado, I can say definitively that an assignment of contract is not illegal. I can't comment on double closings as a viable solution either because I have no experience with the investigative process on that specifically - my experience is only per the assignment of a contract.
Your paperwork is very important. You must clearly stipulate in your contracts that you are not a licensed realtor and do not represent anyone but yourself. I am a principle in every single transaction that I do, and when I assign my position as a buyer, I'm doing it for me. Every single ounce of marketing that I do to find a buyer is for me - not for another or on behalf of another.
If you talk to 10 attorneys they will have 10 different opinions. They can argue any side of the fence if they'd like to, because that's what they're paid to do (I know this well because my dad is an attorney and he can argue any side of an argument if he wants to).
WITH THAT SAID, no matter how legal an assignment of contract is, at any point you can become investigated for it, and you have to go through that process again. It's time consuming and there is a massive "pucker factor." Flat out, it sucks. Also at any point you can be sued by anyone for any reason, and even if you're innocent you'll have to defend yourself. You will prevail, but it will come at an enormous emotional and time toll. So is it worth it? You be the judge. If becoming licensed makes you feel more comfortable, then do so - but if you assign a contract while you're licensed, you're still not representing anyone but yourself so it's the same thing, just with a license to back you (and that license would halt any investigation immediately, so the peace of mind is almost worth it). The choice is yours.