R v. Oersted 2001 BCSC 230 is a useful case dealing with attempt. Basically you can be convicted of attempted to pick an empty pocket - factual impossibility of the offense is not a defence. That said, you cannot be convicted of attempting to commit a crime that does not exist - so the attempt to, say, import sugar into Canada is no offence but attempting to import heroin is.
The Court holds:
 The accused argues that the existence of a real person from whom sexual services may be obtained is an essential element of the offence created by s. 212(4). If that person does not exist, he cannot be convicted of the offence itself, nor of an attempt to commit the offence.
 Section 212(4) incorporates both an attempt and a completed offence in its wording. The argument proceeded on the basis that the elements of an attempted offence set out in s. 24 apply to this specific attempt, and I accept that.
 The elements of a criminal attempt were set out by McIntyre J. in Regina v. Ancio1984 CanLII 69 (SCC), (1984), 10 C.C.C. (3d) 385 (S.C.C.) at p. 401:
…in common law and under the criminal law of Canada criminal attempt is itself an offence separate and distinct from the crime alleged to be attempted. As with any other crime, the Crown must prove a mens rea, that is, the intent to commit the offence in question and the actus reus, that is, some step towards the commission of the offence attempted going beyond mere acts of preparation. Of the two elements the more significant is the mens rea.
 In Regina v. Loewen,  M.J. No. 506 (Q.L.) (Man.Q.B.), Hamilton J., after citingRegina v. Ancio, made the following observation at para 32:
The law of attempt is a separate offence which by its nature may be completed without all elements of the completed offence. Intention is the focus of the offence. And, of course, some elements of the completed offence are required beyond mere preparation.
The trial judgment was overturned on an unrelated ground, 1997 CanLII 4338 (MB CA), (1997) 122 C.C.C. (3d) 198 (Man.C.A.).
 The Crown says that here the accused clearly had the intent to commit the offence and, during argument, the accused conceded that he took steps beyond mere preparation. That is the end of the matter. The accused is guilty even though it was not possible to complete the offence because the girl, Leez, did not exist. The Crown need not establish all of the elements of the offence to obtain a conviction for an attempted offence.
 The Crown says that the accused is trying to recast the defence of impossibility as an absence of an essential element. This cannot succeed in view of the majority decision in United States of America v. Dynar 1997 CanLII 359 (SCC), (1997), 115 C.C.C. (3d) 481 (S.C.C.). InDynar, the accused was charged in the United States with an attempt to launder money, and the American government sought his extradition. He had been the target of an FBI sting operation. A police informer called him in Canada and asked if he would launder drug money obtained from illegal trafficking in the United States. Mr. Dynar agreed to do so. In fact, the money which the FBI planned to transfer to him was "clean" money, which had not been obtained from criminal activities. No transfer of money actually took place and Mr. Dynar was arrested in Canada.
 The issue was whether Mr. Dynar's conduct would also constitute a crime under Canadian law if it were carried out in Canada, thereby satisfying the requirement of double criminality for extradition. In the United States, the offence of money laundering is made out if a person acts on a representation that the money is proceeds of crime, whether or not it actually is. In Canada, the crime requires that the money actually be proceeds of crime. Mr. Dynar raised the defence of impossibility. He took the position that his actions could not be a crime in Canada because the money involved was "clean" money. It was therefore impossible to find him guilty of any completed offence under Canadian law. If he could not be guilty of the completed offence, he argued that he could not be guilty of an attempt to commit the same offence.
 The issue framed by the court was whether an accused who attempted to do the impossible may be found guilty of an attempt. The majority answered this question affirmatively, and found that while Mr. Dynar could not have been convicted of the completed offence, he would be guilty of an attempt to launder money in Canada on the basis of s. 24. At para. 50 Iacobucci J. made the following observation:
In our view, s. 24(1) is clear: the crime of attempt consists of an intent to commit the completed offence together with some act more than merely preparatory taken in furtherance of the attempt. This proposition finds support in a long line of authority. . . . In this case, sufficient evidence was produced to show that Mr. Dynar intended to commit the money-laundering offences, and that he took steps more than merely preparatory in order to realize his intention. That is enough to establish that he attempted to launder money contrary to s. 24(1) of the Criminal Code.
 At para. 62 he went on to consider the distinction between factual and legal impossibility and concluded it was not tenable:
There is no legally relevant difference between the pickpocket who reaches into the empty pocket and the man who takes his own umbrella from a stand believing it to be some other person's umbrella. Both have the mens rea of a thief. The first intends to take a wallet that he believes is not his own. The second intends to take an umbrella that he believes is not his own. Each takes some steps in the direction of consummating his design. And each is thwarted by a defect in the attendant circumstances, by an objective reality over which he has no control: the first by the absence of a wallet, the second by the accident of owning the thing that he seeks to steal.
 He did, however, find a valid distinction between a failed attempt to do something that is a crime and an imaginary crime, stating at paras. 65 - 67:
It is one thing to attempt to steal a wallet, believing such thievery to be a crime, and quite another thing to bring sugar into Canada, believing the importation of sugar to be a crime. In the former case, the would-be thief has the mens rea associated with thievery. In the latter case, the would-be smuggler has no mens rea known to law. Because s. 24(1) clearly provides that it is an element of the offence ofattempt to have "an intent to commit an offence", the latter sort of attempt is not a crime.
Nor should it be. A major purpose of the law of attempt is to discourage the commission of subsequent offences. . . . But one who attempts something that is not a crime or even one who actually does something that is not a crime, believing that what he has done or has attempted to do is a crime, has not displayed any propensity to commit crimes in the future, unless perhaps he has betrayed a vague willingness to break the law. Probably all he has shown is that he might be inclined to do the same sort of thing in the future; and from a societal point of view, that is not a very worrisome prospect, because by hypothesis what he attempted to do is perfectly legal.
Therefore, we conclude that s. 24(1) draws no distinction between attempts to do the possible but by inadequate means, attempts to do the physically impossible andattempts to do something that turns out to be impossible "following completion". All are varieties of attempts to do the "factually impossible" and all are crimes. Onlyattempts to commit imaginary crimes fall outside the scope of the provision. Because what Mr. Dynar attempted to do falls squarely into the category of the factually impossible —— he attempted to commit crimes known to law and was thwarted only by chance —— it was a criminal attempt within the meaning of s. 24(1).
 At paras. 71 and 73, the majority used the example of attempted murder to support their conclusion that an attempt is by its nature an incomplete offence, and the actus reus will always be deficient:
In this, the money-laundering offences are no different from other offences. Murder is the intentional killing of a person. Because a person cannot be killed who is not alive, and because a killing, if it is to be murder, must be intentional, it follows that a successful murderer must believe that his victim is alive. An insane man who kills another believing that the one he kills is a manikin does not have the mens reaneeded for murder. Thus, the successful commission of the offence of murder presupposes both a belief that the victim is alive just before the deadly act occurs and the actual vitality of the victim at that moment. Both truth and belief are required. Therefore, knowledge is required. But this does not mean that the vitality of the victim is part of the mens rea of the offence of murder. Instead, it is an attendant circumstance that makes possible the completion of the actus reus, which is the killing of a person…
The absence of an attendant circumstance is irrelevant from the point of view of the law of attempt. An accused is guilty of an attempt if he intends to commit a crime and takes legally sufficient steps towards its commission. Because an attempt is in its very nature an incomplete substantive offence, it will always be the case that theactus reus of the completed offence will be deficient, and sometimes this will be because an attendant circumstance is lacking.
 At para. 74 the majority concluded that the law of attempt is engaged only when the mens rea of the completed offence is present entirely, and the actus reus is present in an incomplete but more-than-merely-preparatory way. Accordingly, Mr. Dynar could be found guilty ofattempting to launder the proceeds of crime in Canada, even though the money in question was not the proceeds of crime and it was therefore not possible to complete the offence in Canada. Impossibility of completion was not a defence.
But attempt conspiracy is not an offense largely because it is too far from the act to merit criminalization. As the Supreme Court notes in R v. Déry,  2 S.C.R. 669:
47 Given that conspiracy is essentially a crime of intention, and "[c]riminal law should not patrol people's thoughts" (Dynar, at para. 169, per Major J.), it is difficult to reach further than the law of conspiracy already allows. Even if it were possible, it has never been the goal of the criminal law to catch all crime [TRANSLATION] "in the egg", as the Attorney General for Canada has put it in this case (factum, at para. 58). In this sense, conspiracies are criminalized when hatched. And they can only be hatched by agreement.
48 This basic element of conspiracy — agreement — exposes the otherwise hidden criminal intentions of the parties to it. This demonstrates their commitment to a prohibited act. By contrast, the criminal law intervenes later in the progression from thought to deed where someone acts alone. Overt steps are then thought necessary to disclose and establish with sufficient certainty the criminal intention that is an essential element of the attempt to commit an offence.
49 By its very nature, moreover, an agreement to commit a crime in concert with others enhances the risk of its commission. Early intervention through the criminalization of conspiracy is therefore both principled and practical.
50 Likewise, the criminalization of attempt is warranted because its purpose is to prevent harm by punishing behaviour that demonstrates a substantial risk of harm. When applied to conspiracy, the justification for criminalizing attempt is lost, since an attempt to conspire amounts, at best, to a risk that a risk will materialize.