Is it ethical (or legal, if applicable) to say you have a degree in X if your degree was in "X and Y" (single major)? There are departments in many schools that offer "hybrid" majors, such as:


Computer Science and Engineering
Electrical and Computer Engineering
Electrical Engineering and Computer Science
Materials Science and Engineering
Molecular and Cellular Biology
Nutritional Science and Toxicology


etc.

Let us say you earn a degree in the respective area of one of these majors.
For example, let's say you earned an M.S. in Computer Science and Engineering.
Continuing with this example, let's say that down the road, you are asked to certify that you have the degree in one of the majors (say, an M.S. in Computer Engineering).

Are you ethically/legally/etc. (as the case may be) allowed to claim that you have such a degree? Or are you only entitled to claim that you have exactly the degree written on your diploma/transcript and nothing else, even if it seems like a subset of what is written?

Notes:


If the answer differs between the Bachelor's, Master's, or Doctorate degrees, please explain each one.
If the answer is different for different majors, please explain how/why. And if the answer is different in different situations -- e.g. if it is different in different countries -- please explain how and give typical examples for each case, keeping in mind #3 below.
Obviously, in some cases, you may even be technically allowed to falsely claim you have a degree. I am ignoring such cases here; for the purposes of this question, assume I am only talking about cases where it is indeed not okay (either legally or ethically) to falsely claim you have a degree.
My degrees are mostly in the joint subject of Electrical Engineering and Computer Science. Past undergraduate, however, I pretty much exclusively studied in the computer science side of the department. Thus, I find it appropriate and accurate to describe myself either as having EECS degrees or CS degrees, but would not claim to have EE education past undergraduate. Likewise, my CS education included enough hardware and systems education that I am comfortable saying I received CE education. 

I think a similar analysis can be applied to any composite major. Most people and institutions understand that department names vary across institutions, so as long as you do not attempt to deceive about the skills you gave, it should be OK.