Actually, no that is incorrect. As Dwayne pointed out, once they move onto becoming a threat to your personal safety, the bets are off. A combative individual can "decline" an IV all they want, if they are a danger to themselves and / or others, they are getting an IV providing it can be accomplished safely and efficiently. In many cases, asinine behavior can be predicted in the attention seeking population. Because of this and the very nature of psychological disease, I will usually establish an IV while on scene with adequate assistance available should the individual have a differing belief of the appropriate course of action.
One that really sticks in my mind was an addict high on PCP. Dude was carrying 4 cops on his back. 10mg of Versed
IM didn't phase him.....................But the 200mg of Anectine IM eventually did. Sometimes you just have to improvise to insure you go home safely at the end of your shift.
Again, the OP needs either appropriate sedation options or a better transport policy.