Oh also when a substance is illegal you need to consider where you're getting the substance from. Is your money helping gangs etc?

I think this question can be broken down some:

1. Is doing anything illegal immoral?
2. Is marijuana consumption immoral?

1. Typically in democratic societies, laws are created and enforced by society for society. In some ways laws can be thought of as an agreement between individuals in a society and the state/government. So if something has been deemed unhelpful or harmful to a society and its values to the extent it has been written into law, then it must be immoral to commit acts of civil disobedience in a democracy where it is assumed there are peaceful and constructive ways to contest law...right?

Well yes and no.

For civil disobedience to be considered immoral you would have to at least assume there was no bias in democracy however, with many first world democracies being a result of colonialism, the foundations of our current day laws are already biased. So as has been the case with cultural revolutions, be they race, gender, or class related, civil disobedience is sometimes the only way for the minority to be heard.

For something to have moral value, more than one sentient being needs to be present otherwise we're left with the moral equivalent of the proverb "if a tree falls in the woods with noone to hear it, does it make a sound."

So, from the viewpoint of civic duty - no you don't always have to follow the law to be moral, but are you not following the law in order to achieve a greater good? If you're using marijuana privately and noone knows about it, does it matter?

2. Marijuana is a psychotropic drug which alters brain activity. On a scale of intensity I'd put this substance on the 'mid to low' end of the scale. I think like other substances that alter the biochemistry of people, the morality of use is context dependent. Like Alcohol in certain amounts at specific occasions seems to be ok, in contrast large amounts too often leads to anti-social behaviour, dysfunction and even permanent physical damage/death. With Marijuana I think if you have reasonable amounts, at reasonable intervals and you can still function well in your roles (as a family member, parent, student, employee etc) then it is fine. I'd link Morality with responsibility for substance taking. If your substance isn't negatively impacting on the quality of your life and those around you, then I think it is morally acceptable to break the law and fight for legalisation should there be proven benefits of taking the substance. If your habit is out of control and you become a burden on society then I think it becomes immoral to continue to take the substance and it would be immoral to take at any point after it has been established you have a problem.