I agree you can sell any domain you bought an hour ago.
However, if you are unable to transfer the domain to the new owner during a "reasonable" time, there could be problems.
i.e. it will be necessary to ensure you can transfer to the purchaser at the existing registrar, or the purchaser will have to be agreeable to waiting until the 60 days are up before they get possession of the domain. DNS can of course be changed as an interim measure to give the new owner effective use of the domain while they wait.
I don't think it is all that fair to spring the fact upon the purchaser, once they have already paid, that they can't actually have the domain for another 60 days.