How to describe "choose to do something by one's own willing"

Question

For example, there is a course (say French course), for students in a college. The students can take it, but they don't have to. Someone, who is not a student in that college, thinks that this course is optional. But he saw, on a student's facebook wall, that "I have a french course." So he wants to ask this student that if this course is optional.

Of course he can just ask: Is this course elective/optional?

But the above is just an example to describe the words or the expressions that I need: An expression that says One can choose to do a particular thing by his own willing.

There is a constrain for such expressions:

If a thing breaks the law or the rules (of a society, company, school...), then we can't use this expression for such a thing.

I am not sure if ... can do...by ...own willing is a common expression for this. Furthermore, is there any other/short way to express this?

Answer 1

You can use the expression "You can do it of your own free will" or "You can do it of your own volition", or simply "It is voluntary", in other words, "It is not compulsory", to describe things that are volitional.

Answer 2

"By... own willing" does not even exist as a way of saying this. It is not a usable phrase, and you should eliminate it as something you would ever say or write.

To come close to the concept you want, you might want to use "of one's own accord," or "on one's own initiative."

Answer 3

Even simpler: delete “By ... own willing” from the phrase in the question, and end with “One can choose to do a particular thing.”  For example, “Did you choose to take that French course?”

In some situations, where freedom of choice might be assumed to be obvious, this might be interpreted to mean, “Did you do that particular thing?”  For example, “Did you choose to have wine with dinner?”  To place the emphasis on the elective aspect of the behavior, one might ask, “Did you take that French course by choice?”

P.S. “I have a French course” is not common usage; one would say “I have taken a French course”, “I have studied French”, or perhaps even “I have taken French.”  (Or, using simple past tense, “I took a French course”, etc.)