There is such a thing as Congressional oversight. Also, in caes where an individual can prove actual harmed from abuse of the program, he would have standing to sue. That's the problem here. These plaintiffs cannot point to any actual harm, but only fear or speculation that they might be harmed. Any harm is, at best, potential but not demonstrably actual. In legal terms, they lack standing (which the constitution requires before an Article III judge can rule on it). The court lacked constitutional power even to hear the case and should have thrown it out for that reason alone.
So, if the ACLU was able to prove that they were unfairly targeted under this program, would they be able to sue the members of the House Select Committe on Intelligence, for example, for failing to provide oversight? For example, could they take Nancy Pelosi to court for her role, or negligence, in the case?