Yes, ʻōhiʻa can be sold legally for firewood; however, please handle the wood and advertising responsibly to avoid spreading Rapid ʻŌhiʻa Death (ROD) disease.
Within the Island of Hawaiʻi there are no legal restrictions to moving or selling ʻōhiʻa. The Hawaiʻi Department of Agriculture quarantine restricts shipping of ʻōhiʻa off Hawaiʻi Island, which means any piece of ʻōhiʻa (log, posts, foliage, etc.) has to be tested free of ROD disease before moving off the island.
We highly recommend that people not move ʻōhiʻa firewood or posts because moving infected wood can indeed spread ROD. The best practice for firewood is to not move ʻōhiʻa wood out of your neighborhood.
If you sell ʻōhiʻa wood, be transparent in your advertising. If you aren't certain of the presence of ROD, say so as a disclaimer. Let buyers or potential buyers know that the current recommendation is to keep ʻōhiʻa wood in your neighborhood.
When cuting ʻōhiʻa, keep saw cuts to a minimum to avoid creating a lot of fine particles. Once wood is bucked up, use an axe to cut the wood into pieces suitable for firewood. If the wood will be cut up at another location, the buyer should be aware of the risk of spreading ROD by cutting at the new location, especially areas of mostly healthy ʻōhiʻa forest.