There is more than a grain of truth to this. But as CLS evolved and began to dialogue with its offspring in the race and feminist movements, a counterthread began to emerge. This talk of rights and justice and ideals is certainly not immune to being enlisted in the service of regression. But, as many veterans of the civil rights movement noted, the fact that legal discourse was constructed around these categories meant that they had grounds to at least make claims. Rights were something Black people could stake out, and it is an inherently superior frame for the debate than "pure" power politics. Because law channels elite discourse into terms like justice, advocates can choke them with those words. "How can you do this?" can easily be responded to with "Because I can." "How can you call this just?" is not as easy to dodge out of.
The relative autonomy of law from politics-- rather than its complete autonomy-- simultaneously posed a threat and a promise. The threat was that law would fail to do much more than ratify and legitimate the interests of the powerful; the promise was that it could hold off the worst excesses of power by giving people discursive and institutional tools to talk back to power, to restrain its selfishness and inhumanity, and to imagine finer, better visions of human association.
The threat and the promise of law were joined together inseparably. What gave law its power to legitimate was its ability to re-describe unjust and unfair events, social practices and institutions in terms of valued ideals of human association like consent, freedom, equality and fairness. In the hands of lawyers and politicians, law could disguise, mystify and legitimate great injustices using the very ideas and ideals we admire. But law could only do this because it appealed to these values and claimed to be trying to put them into practice through law. That is, the recourse to law forced the powerful to talk in terms in which the powerless could also participate and could also make claims.
The CLS critique of law was thus Janus-faced. On the one hand, powerful people used law to subordinate others and secure their own interests under the guise of promoting laudable goals like freedom, equality, liberty, consent, community and human dignity. On the other hand, by choosing to speak in the language of law, powerful people and interests could be called to account because they tried to legitimate what they were doing in these terms. The people they took advantage of could always argue that this was a misuse of law, an illegitimate attempt at mystifying rhetoric. They could then appeal to the values that law sought to protect to promote better, juster, and more humane practices and forms of human association.
Law is often overstated as a tool for liberation. But then, it is often underestimated as well. Law has the ability to force the discussion into terrain advantageous for liberators. It does not guarantee results, but it may make the fight just a little fairer.