1)
What does the Navi come to say?
1.
Radak: He returns to rebuke them for doing evil to the Aniyim ? "l'Oyev Yekomem" (2:8).
2.
Malbim: This replies to "ha'Katzar Ru'ach Hashem Im Eleh Ma'alalav" (2:7). Refer to 3:1:2:2.
2)
Why does he specify "Roshei Yakov u'Ketzinei Beis Yisrael"?
1.
Radak: The complaint is against you ? "you should know the Mishpat", to save the victim from theft and oppression!
2.
Malbim: He tells them, you yourselves judge if they deserved to be punished from Hashem ? "you should know the Mishpat!"