I am not grammar or punctuation expert and do not pretend to be, but I would add 'that are ' if I were saying this sentence

I agree with Robbyn 100%. Don't add that are unless you want to change the meaning.

Adding "that are" to that part of the sentence changes the meaning of the sentence and requires that you add "on" to the sentence before "Congressional." "During his tenure as Chief Justice, John Marshall ruled that the Supreme Court has the power to rule Congressional acts unconstitutional," means that the Supreme Court can look at Congress's acts, declare them unconstitutional and say they cannot be enforced. It means that the Supreme Courts gets to judge whether Congress has the right to do certain things. "During his tenure as Chief Justice, John Marshall ruled that the Supreme Court has the power to rule on Congressional acts that are unconstitutional," means that the acts have already been deemed unlawful, and the Supreme Court gets to decide after the fact either that they were unlawful, or what the punishment will be. The two sentences do not mean the same thing.