The Scottish government said Tuesday that it would hold a referendum on independence from Britain in 2014, a decision that Alex Salmond, below, who leads the government in Edinburgh, said would be Scotland’s “most important decision for 300 years.” But the path to the referendum promises to be tortuous. Prime Minister David Cameron’s government in London told Parliament that it had the sole constitutional right to approve a referendum, but that he was prepared to devolve the power to the Scottish authorities on terms that would make the referendum result “legal, decisive and fair.” Mr. Salmond said he would hold a referendum on his terms. The Cameron government has said it wants an earlier date for the vote, to end uncertainty that it says is deterring investment in Scotland. The British government also said the question should be a straightforward yes or no on independence, without the third option Mr. Salmond wants on the ballot, which would give Scotland full autonomy as part of Britain.