UFC heavyweight champion Jon Jones isn't tapping out in his ongoing legal battle ... entering a not-guilty plea for the two misdemeanor charges he's facing in relation to a drug test gone wrong earlier this year.
Jones -- who appeared in New Mexico court virtually -- was charged with assault and interference with communications earlier this week ... after a testing agent claimed he made threats and took their cell phone when they popped up at his Albuquerque home unannounced back in March.