canada has much stricter laws. i've posted here about some of the ways that you can get around those laws. i don't think writing more laws is the answer in either country.
what i'd like to see is transparency, and a culture that upholds it. so, if a candidate wants to take money from wall street or the oil industry or the weapons industry, then that's ok - so long as they tell me so i can look it up. i would be highly unlikely to vote for such a candidate on the basis of them having a conflict of interest. that's what we need, here: a culture that rejects conflicts of interest as unacceptable, not more laws to be dodged while an apathetic voting base shrugs. jefferson articulated this position by calling for an educated populace.
so, when sanders says he wants to take money, it doesn't bother me a priori. but, i would push him to ban anonymous contributions and to lead the way in transparently publishing the source of every dime that comes in. i want who, how much and (where possible) why. that way, the media and the public can see for themselves where the money is coming from and decide whether a conflict of interest exists. it would be in the organization's interest, then, to be careful about who it accepts money from. but, that's a part of building trust in good governance.
"the cornerstone of democracy rests on the foundation of an educated electorate." - thomas jefferson