A person with a strict interpretation of the constitution wants the government to only perform the powers given to them in the constitution. If the constitution does not explicitly give the power to an individual or group (like the President, Congress, or the Supreme Court) than that group/individual can not perform that duty.
On the other hand, those individuals who think that the constitution is flexible and that some powers can be "assumed" would fall under the category of having a loose interpretation of the constitution.
