In Canada, the doctrine of parliamentary supremacy is the rule. A written Constitution is a recent addition.
In a minority parliament, the legislature can be a very effective check in reality.
Executive (Crown powers) are also distributed by the Governor General to the entire cabinet. Depending on the relative strength of the politician, they are technically colleague — unlike the American system where they work for the president. The Canadian prime minister are usually in fact and in legal form “first among equals.”