The executive is simply an agent of the Legislative will and has no say in the interpretation of laws. In fact the Executive may be removed by the legislative if the Executive is adjudged to have badly executed the Law of Nature. Likewise, while the Legislative may be the supreme power it is still limited as to what it may do by the Laws of Nature. Locke believes that the legislative body need not be "always in being" and it is not "so much as convenient that it should be". Locke states that "the laws that are at once, and in a short time made, have a constant and lasting force, and need a perpetual execution, or an attendance therein.and thus the Legislative and Executive power come often to be separated" (Locke, 144). the separation of powers of which Locke speaks is therefore also a result of the different periods of active responsibility that are required from the respective institutions, as well as a limitation of power.
Locke argues that it would not at all be ideal to have a situation whereby any man has a hand in both the Legislative and Executive branches of government. Locke feels that in this case the man would consider himself supreme. "it may be too great a temptation to human frailty, apt to grasp at power, for the same persons, who have the power of making the laws, to have also in their hands the power to execute them, whereby they may exempt themselves from obedience to the laws they make." and thus in Locke's terms he believes that said person may "come to have a distinct interest from the rest of the community, contrary to the end of society and government." (Locke, 143).
This is coming back to the idea of too much power going to a single person, which could be, Locke believed to be to the detriment of society. Locke finds it in mans nature to become greedy when put in to a position of total control. It is upon this assumption that he feels the two sections of government should be kept distinct and separate in the interests of the community.
