Since the Watchtower article of 1929 the understanding of "the powers ordained of God" has changed (in 1962) to apply to the governments of this world. So, if the prohibition of alcohol were to occur today Jehovah's Witnesses would have a different view and (officially) obey it.
This doesn't really answer your question about ingesting legal cannabis for recreational use but their current view of using snuff (which does not differentiate from smoking tobacco) suggests it would be forbidden. The book Shepherd the Flock of God, April 2020, says:
However,a judicial committee is required for a practice of abusing addictive drugs, including betelnut, marijuana, and tobacco. (2 Cor. 7:1; w06 7/15 pp.30-31; lvs pp.110-117)