“Because of its special importance, the Sunday celebration gives way only to solemnities or feasts of the Lord.”
—General Norms for the Liturgical Year and Calendar, Chapter 1, Title I, Section II, Item 5
The Sunday feast takes precedence over ALL liturgical events save solemnities and even more major feasts.
You would be surprised by how long I have been looking for the legal basis for the Catholic practice of suspending any fast (including the Lenten fast) when it falls on a Sunday. I posted this on Facebook last night and realized that I may not be the only one who wondered about it. There’s the norm, in black and white, for the Google robots to find. Hope it helps somebody else out there clear it up.
There may be other Church law on this subject, and I would welcome anyone in the comments telling me where I can find it.