Since the patriation of the Constitution in 1982, a more complete amending formula has been adopted in the Constitution Act, 1982, in sections 38 to 49.
Amendments can only be passed by the Canadian House of Commons, the Senate, and a two-thirds majority of the provincial legislatures representing at least 50% of the national population (the 7/50 formula). Though
not constitutionally mandated, a popular referendum in every province is also considered to be necessary by many, especially following the precedent established by the Charlottetown Accord (see below).
If a constitutional amendment only affects one province, however, only the assent of that province's legislature is required. Eight of the ten amendments passed so far have been of this nature, with four passed by and for Newfoundland and Labrador, one passed for New Brunswick, one for Nunavut, one for Prince Edward Island, and one for Quebec. Some of the above did also require approval by the federal Parliament under section 43(b) due to the English and French nature of the amendment.
There are
some parts of the Constitution that can only be modified by a unanimous vote of all the provinces plus the two Houses of Parliament, however. These include changes to the composition of the Supreme Court of Canada, changing the process for amending the constitution itself, or
any act affecting the Offices of the Canadian Monarch or Governor General.
Source:
http://en.wikipedia.org/wiki/Amendments_to_the_Constitution_of_Canada#Amendment_formulas