I should add some comments to the summary of Akulue v R posted here on 19 September 2013.
Akulue concerns an affirmative defence. That is, a defence that is pleaded in answer to a proven allegation of actus reus and mens rea. The defendant in advancing an affirmative defence is saying, "Yes, if it is proved that I did the prohibited thing (or that I omitted to do what I had a legal duty to do) and that I had the proscribed state of mind, I am nevertheless not responsible because of these additional circumstances." Indeed, the defendant will almost always be conceding that he did the prohibited thing, or omitted to perform the obligation, with the proscribed state of mind.
And Akulue is about one affirmative defence: compulsion, a codified form of necessity. Another codified form of necessity is self-defence and defence of another. But in compulsion the threatener's objective is the commission of the offence in respect of which the defence is subsequently advanced:
R v Ryan, 2013 SCC 3 (noted here on 31 January 2013). The Supreme Court in Akulue was referring only to compulsion when it said  that the legislation is intended to "codify exclusively the circumstances in which compulsion by threats of harm from another person provides a defence, leaving only other circumstances of necessity to the common law." That is to say, necessity in the form of force of nature, act of god, or other overwhelming force not originating in another person, may be a defence, although the defendant will be expected to demonstrate fortitude (if anyone is not thinking about R v Dudley and Stephens, where a defence of necessity failed, they should go back to law school).
When threats negative mens rea
In contrast to affirmative defences are disputes about the existence of elements of an offence. A contention that specified circumstances cast doubt on the existence of an element of an offence, is not strictly speaking a "defence", although it is common to say that the person's defence was that he did not do a prohibited thing, or omit to do a legally required thing, or that he did not have a required state of mind. This usage of the term "defence" is just a convenient way of describing why a charge was denied.
Usually an intention, however reluctantly it may be entertained, is still an intention. Threats do not usually negative mens rea. Recklessness is also usually a sufficient state of mind for liability, and, however it may be defined, it is not negated by a hope that the proscribed consequences will not occur. But a few offences require more than intention.
There is some authority for the proposition that an element of the offence of possession of a controlled drug is a willingness to exercise control over that drug: R v McIntyre 9/3/79, CA94/77, Warner v Metropolitan Police Commissioner  2 AC 256;  2 All ER 356 (HL) per Lord Morris at pp 296, 375 referring to the need for the defendant to be "assenting" to being in control of the drug. This willingness is an additional element to that of animus possidendi, as an intention to exercise control is sometimes called. The intention must be willingly entertained.
Willingness to exercise control over a drug may be negated by threats of dire consequences for failure to do so, as was the position in McIntyre. There, the threats of physical harm would not have satisfied the requirements of the affirmative defence of compulsion, because they lacked immediacy, but the Court of Appeal held that they did negate the element of willingness, which it described as a "voluntary assumption of control" over the drug.
Does Akulue change this?
The offences alleged in Akulue – importing methamphetamine and conspiring to supply methamphetamine - were not offences of possession, and they did not, as far as is currently known, have elements of willingness to exercise a relevant power. A defendant can participate in an importation of a drug without ever having had possession of it, and a person can agree to commit an offence even if he is reluctant to enter that agreement. Usually, mere reluctance does not negate an element of an offence.
It is possible that the offence of permitting premises to be used for the commission of a drug offence is another offence that has an element of willingness. Does one "permit" unwillingly? A defendant must do what is reasonable to prevent the offending - R v Sweeney  2 NZLR 229 (CA) – but arguably, reasonableness will be judged in the context of circumstances that may have negated the defendant's willingness.
So, Akulue is about the affirmative defence of compulsion, not about those rare offences where willingness is an element of mens rea.