Our written Constitution  'Declares' certain rights of the men & women of this nation.
It's important that people understand that these rights belong to men & women *not* as 'members of SOCIETY', but as INDIVIDUALS: 
By the absolute rights of individuals we mean those which are so in their primary and strictest sense; such as would belong to their persons merely in a state of nature, and which every man is entitled to enjoy whether out of society or in it.
But with regard to the absolute duties, which man is bound to perform considered as a mere individual, it is not to be expected that any human municipal laws should at all explain or enforce them. For the end and intent of such laws being only to regulate the behavior of mankind, as they are members of society, and stand in various relations to each other, they have consequently no business or concern with any but social or relative duties.
Let a man therefore be ever so abandoned in his principles, or vicious in his practice, provided he keeps his wickedness to himself, and does not offend against the rules of public decency, he is out of the reach of human laws.
And what are these rights? From the same source as above:
Thus much for the declaration of our rights and liberties. The rights themselves thus defined by these several [Ed: Declaratory] statutes, consist in a number of private immunities; which will appear, from what has been premised, to be indeed no other, than either that residuum [remainder] of natural liberty, which is not required by laws of society to be sacrificed to public convenience; or else those civil privileges, which society has engaged to provide, in lieu of the natural liberties so given up by individuals.
These therefore were formerly, either by inheritance or purchase, the rights of al mankind; but, in most other countries of the world being now more or less debased and destroyed, they at present may be said to remain, in a peculiar and emphatic manner, the rights of the people of England. And these may be reduced to three principal or primary articles;
the right of personal security, the right of personal liberty; and the right of private property:
Because as there is no other known method of compulsion, or of abridging man's natural free will, but by an infringement or diminution of one or other of these important rights, the preservation of these, inviolate, may justly be said to include the preservation of our civil immunities in their largest and most extensive sense.
The right of personal security consists in a person's legal and uninterrupted enjoyment of his life, his limbs, his body, his health, and his reputation.
Cannabis is a medicinal herb, I know because it stops my migraine attacks 100% (it really does work!).
I also suffer with a painful arthritic condition, Cannabis helps ease the pain & swelling.
I assert that the Prohibition of Cannabis via the Misuse of Drugs Act, which is a Remedial Statute, violates my constitutional right to personal security, my health, and in enforcing such an Act, my right of liberty & property would be violated also. So a complete violation of all 3 main Constitutional rights, this is not acceptable.
Proof that our Constitution does not recognize PROHIBITION can be found from a speech given on the 23rd May, 1628 by Sir John Glanville to a committee of both Houses of Parliament, in the Painted Chamber at Westminster, on the liberty of the subject:- 
Glanville was concerned by phrases in the draft for the bill which pretty much gave the MONARCH overriding powers, the phrases were "unless it be by sovereign power.", his reasons (I believe) for excluding them (and they were exluded from the final bill!) was that the people would fall back on to their Constitution if the MONARCH acted arbitrarily, quote:
My lords, as there is mention made in the additional clause of sovereign power, so is there likewise of a trust reposed in his Majesty, touching the use of sovereign power.
The word "Trust" is of great latitude and large extent, and therefore ought to be well and warily applied and restrained, especially in the case of a king: there is a trust inseparably reposed in the persons of the kings of England, but that trust is regulated by law.
For example, when statutes are made to prohibit things not mala in se [because they're intrinsically bad], but only mala quia prohibita [conduct that is prohibited by laws, although not inherently evil], under certain forfeitures, and penalties, to accrue to the king, and to the informers that shall sue for the breach of them; the Commons must and ever will acknowledge a regal and sovereign prerogative in the king, touching such statutes, that it is in his Majesty's absolute and undoubted power to grant dispensations to particular persons, with the clauses of non obstante, to do as they might have done before those statutes, wherein his Majesty, conferring grace and favour upon some, doth not do wrong to others.
But there is a difference between those statutes, and the laws and statutes whereupon the petition is grounded: by those statutes the subject has no interest in the penalties, which are all the fruit such statutes can produce, until by suit or information commenced he become entitled to the particular forfeitures; whereas the laws and statutes mentioned in our petition are of another nature; there shall your lordships find us rely upon the good old statute, called Magna Charta, which declareth and confirmeth the ancient common laws of the liberties of England: there shall your lordships also find us to insist upon divers other most material statutes, made in the time of Kings Edw. III. and Edw. IV., and other famous kings, for explanation and ratification of the lawful rights and privileges belonging to the subjects of this realm: laws not inflicting penalties upon offenders, in malis prohibitis, but laws declarative or positive, conferring or confirming, ipso facto, an inherent right and interest of liberty and freedom in the subjects of this realm, as their birthrights and inheritance descendable to their heirs and posterity; statutes incorporate into the body of the common law, over which (with reverence be it spoken) there is no trust reposed in the king's "sovereign power," or "prerogative royal," to enable him to dispense with them, or to take from his subjects that birthright or inheritance which they have in their liberties, by virtue of the common law and of these statutes.
Regarding the recreational use of Cannabis, I'd like to leave you with the first paragraph from 'Vices are not Crimes by Lysander Spooner' available online here
Vices are those acts by which a man harms himself or his property.
Crimes are those acts by which one man harms the person or property of another.
Vices are simply the errors which a man makes in his search after his own happiness. Unlike crimes, they imply no malice toward others, and no interference with their persons or property.
In vices, the very essence of crime – that is, the design to injure the person or property of another – is wanting.
It is a maxim of the law that there can be no crime without a criminal intent; that is, without the intent to invade the person or property of another. But no one ever practises a vice with any such criminal intent. He practices his vice for his own happiness solely, and not from any malice toward others.
Unless this clear distinction between vices and crimes be made and recognized by the laws, there can be on earth no such thing as individual right, liberty, or property, and the corresponding and coequal rights of another man to the control of his own person and property.
For a government to declare a vice to be a crime, and to punish it as such, is an attempt to falsify the very nature of things. It is as absurd as it would be to declare truth to be falsehood, or falsehood truth.
Thank you for taking the time to read my unique angle on this extremely popular issue.