Disclaimer: the sum total knowledge of the freedom riders that I have is from reading the wikipedia page on them just now, so I don't hold myself out as any kind of expert here.

Because you asked for my opinion, yes, I do consider their actions as working with the system of laws (obviously) and public mores.

I believe they had federal law on their side and were seeking to make the changes in real life that the law demanded. In that regard, they were working even more within the system than Rosa Parks.