2013 (SC 2013, c 6). One section of the amending formula, section 41, says that "the legislature of each province may exclusively make laws amending the constitution of the province". This might entrench some pre-Confederation legislation concerning the colonies that are now Canadian provinces, but that same section allows the provinces to amend the legislation unilaterally despite them being part of the constitution. Unwritten constitutional sources Some constitutional rules in Canada cannot be found in any of the above documents, and have been ruled to be implicitly part of the Canadian constitution by the courts. Many of these rules are old British conventions that were incorporated into Canadian law by the preamble of the Constitution Act, 1867, which says that the Constitution should be "similar in Principle to that of the United Kingdom", much of which itself is unwritten. There are three general sources of unwritten constitutional rules: conventions, royal prerogative, and unwritten principles. The first type of unwritten source is constitutional conventions. This includes the role of the Prime Minister of Canada, which was not mentioned in the Constitution until 1982, and even then only in passing. It also includes the fact that the governor general in most circumstances is required to grant Royal Assent to bills adopted by both houses of parliament, and the requirement that the prime minister either resign or request a dissolution and general election upon losing a vote of confidence in the House of Commons. Many of unwritten rules based on the preamble concern the procedure for how the Parliament of Canada and the Assemblies of its provinces are run. For example, in the case New Brunswick Broadcasting Co. v. Nova Scotia (Speaker of the House of Assembly), the Supreme Court of Canada ruled that parliamentary privilege is a part of the unwritten convention in the Constitution of Canada, which means that Parliament may use parliamentary privilege to take certain actions even though they violate another part of the constitution. Most of these procedures have never been addressed by the Supreme Court, so it is not clear which ones form part of the constitution. The second type of unwritten source is the royal prerogative: reserve powers of the Canadian Crown, being remnants of the powers once held by the British Crown, reduced over time by the parliamentary system. Primarily, these are the Orders in Council, which give the government the authority to declare war,