an "X is an X is an X" what does this mean?

I am reading https://openparliament.ca/bills/42-1/C-6/ (I must say, with great delight but that's not relevant) and

Canadian is a Canadian is a Canadian

A citizen is a citizen is a citizen.

I do not understand this structure. Why not just "A citizen is a citizen"? What is the meaning of repeating this?

It usually means an X is an X and will never be anything other than an X - reinforcing the idea with repetition. If you look only at the number of words and think all repetitions are tautological (that is, they add no further meaning), then surely the extra "is an X" is unnecessary. But sometimes repetition underlined or strengthens a point.

However, the context you're supplying discussing Canadian citizenship, dual citizenship, etc. makes this more subject to interpretation. The relevant parts of the discussion surrounding these statements should be edited into your answer (one shouldn't have to read the entire house bill to get to those quotes.) :-)

The first example of this structure that I can remember is "A rose is a rose is a rose" written by Gertrude Stein (in several different pieces).

While I wouldn't want to interpret exactly why Stein used this construction, (It is discussed briefly in Wikipedia), what it most commonly means today is that an X is inexorably X, that is, driving home that fact by repetition. One of the times she used the construction was in a story about a girl named Rose:

Rose was her name and would she have been Rose if her name had not been Rose. She used to think and then she used to think again.

Would she have been Rose if her name had not been Rose and would she have been Rose if she had been a twin.

Rose was her name all the same and her father's name was Bob and her mother's name was Kate and her uncle's name was William and her aunt's name was Gloria and her grandmother's name was Lucy. They all had names and her name was Rose, but would she have been she used to cry about it would she have been Rose if her name had not been Rose. (The World is Round)

It seems to follow Shakespeare's observation that

A rose by any other name would smell as sweet (Romeo & Juliet)

Shakespeare is saying very poetically that a rose, regardless of what it is called, is still a rose; it still smells as sweet, is still beautiful, etc.

Gertrude Stein's line, which she obviously liked, is less (Romantically) poetic but a lot more direct.

_{Stein's Rose
GERTRUDE STEIN: THE WORLD IS ROUND}