Question

Regarding the authority of an authority to expand its own boundaries, I was reminded of something from Reiner’s book on Rabbeinu Tam. The question is whether from the claim, “Body A has no authority to legislate Law B, and therefore presumably the body did not legislate Law B,” one may infer that even if the body did in fact legislate Law B, the legislation is void. Or is it possible—of course only for certain kinds of bodies—that the body does in principle also have authority to expand its own powers, except that this is less likely, and so in the absence of knowledge we would assume that is not the case.
It is always easier to discuss a case, so I will describe it in numbered sections. The question is whether the alternative explanation I wrote in section 5 seems plausible to you.
 

1. In chapter 5, Reiner discusses Rabbeinu Tam’s attitude toward the Geonim (and concludes, somewhat surprisingly, that Rabbeinu Tam treated their words with respect but did not grant them absolute authority). At the beginning of the chapter, Reiner discusses a rebellious wife who says, “He is repulsive to me” (Sefer HaYashar, responsa 24). Rabbeinu Tam rules that according to the law of the Talmud, one does not compel the husband to give a bill of divorce immediately (without the ketubah), but only after twelve months. Rashbam cited the enactment of the Geonim that when she says, “He is repulsive to me,” they give a bill of divorce immediately, and Rashbam understands this to mean that they compel the husband (as the Geonim apparently really did intend). Rabbeinu Tam responds to him that the Geonim have no authority to advance coercion of a bill of divorce, since a bill of divorce given through unauthorized coercion is an invalid bill of divorce, and the Geonim have no power to validate a bill of divorce that the Talmud invalidates, and therefore this is an enactment that increases the number of mamzerim.

1. Reiner understands that Rabbeinu Tam knew that the Geonim really did enact immediate coercion—that is, that the Geonim themselves certainly thought they had authority to enact immediate coercion—and that Rabbeinu Tam disagrees with them about the limits of their authority. [Reiner then explains, characteristically, that although Rabbeinu Tam attributed great importance to the words of the Geonim and held them in very high regard, as Reiner infers from other citations, here in the case of the rebellious wife Rabbeinu Tam was immersed in a “deliberate effort to prevent coercion of a bill of divorce” and therefore ignored the authority of the Geonim. Wonderful.]

1. In my opinion, anyone who looks carefully at Rabbeinu Tam’s words (Sefer HaYashar, responsa 24, cited above) will see clearly that Rabbeinu Tam says it is not within the Geonim’s authority to enact immediate coercion, and therefore Rabbeinu Tam assumes that the Geonim indeed did not enact something beyond their authority. In other words, they did not enact toward the religious court that there should be immediate coercion, but only enacted toward the husband that he must give a bill of divorce immediately. For there Rabbeinu Tam goes on and explains, in line with his own view, the words of the Rif and the Halakhot Gedolot—they wrote that they “give a bill of divorce immediately,” and Rabbeinu Tam explains that this means they give the bill of divorce with the husband’s consent, without coercion—and he is aided by the words of Rabbenu Chananel.

1. Suppose my interpretation is correct, and Rabbeinu Tam did not directly disagree with the Geonim about what the boundaries of their authority were—that in their view they had authority to advance coercion of a bill of divorce, while in his view they had no such authority—but only said: “They do not have authority for a certain statement, and therefore presumably they did not make that certain statement.” Can one indeed infer from this that even if we discover that that authority did in fact make that certain statement—as it seems to me is now clearly known, that the Geonim did indeed enact coercion and not merely the husband’s consent—then Rabbeinu Tam disagrees with them and holds that this was beyond their authority? In other words, was Reiner right in this sense, that Rabbeinu Tam clearly limits the authority of the Geonim to enact ordinances?

1. At first glance, even after one knows that the Geonim did indeed enact early coercion, Rabbeinu Tam’s view is before us that they had no authority for this. But there is another side to it, and that is what I am asking your opinion about—Rabbeinu Tam thought they had no authority for this, and therefore assumed they did not exceed their authority, and interpreted their enactment to mean that they intended to instruct that the bill of divorce be given immediately, but not under coercion. But perhaps Rabbeinu Tam also agrees that if the Geonim did in fact enact it—that is, they hold that this is within their authority—then in this dispute over the limits of authority, there is some weight to the Geonim’s own decision to expand their authority. To me that does not seem paradoxical, but perhaps I am mistaken and you will explain.