One of the issues raised by those who oppose renewing the commandment of Tekhelet rests on the argument that we no longer have the tradition.
In an article at
http://www.vilnagaon.org/solutions.htm section 16 this issue is discussed.
16 Renewing an Object of a Mitzva Without Tradition
Since there is no agreement among the Rishonim on the matter of how to exactly perform the Tekhelet tests and there isn't full agreement among the Achronim concerning from which Chilazon did they extract the Tekhelet dye material in the past and so too there isn't 100% on how to dye, perhaps someone might contend that if so the mitzva of Tekhelet has the status of an object of a mitzva without a tradition.
If so, I will relate as a matter of principle to the question, is it possible to renew the mitzva of Tekhelet or other mitzvas {or to be more loyal to the Hebrew plural of the word, mitzvot or in English commandments} without a tradition.
In the responsa of Moharil Hachadashot, to Orach Chaim, siman 5 it is written that one can renew the Mitzva of Tekhelet based on the signs that the Chilazon fish has. This implies, that there is not a need for a tradition. And also in a general way I wish to bring proof that we are obligated to renew mitzvas that are similar to Tekhelet, even though we do not have an oral tradition passed down from one man to another.
In the responsa of Shvut Yaacov, part 1, siman 36 starting with the words "Ol Davar" the author informs us, which Hadassim should be used for the mitzva of Hadassim for the holiday of Succot when faced with several options. Option 1] Newly found Hadassim that grow in the city of Prague which are moist and have 3 petals emanating from the same height on the branch which do not crumble when a fingernail touches the leaves. But on the other hand there is no oral tradition about these Hadassim and there is a small possibility that these Hadassim were interbred with a different tree or bush, thus invalidating them for Succot. Option 2] To use the Hadassim that our ancestors have been accustomed to use, which are brought from a distant land and arrive in the state where the leaves are not yet white, but are indeed brittle breaking under the pressure of a fingernail. In this stale state there is a difference of opinion if the Hadassim are kosher for Succot and one would have to rely on Raavad and the Poskim, that as long as the leaves are green and haven't whitened it is kosher.
Shvut Yaacov concludes that when option 2 and option 1 are both available, one must use option 2. He criticizes the haughtiness and too daring spirit of Chakham Tzvi for ruling in favor of option 1 because "do not depart from the Torah of your mother, ask your father and he will tell you, your elder one and he shall tell you" {quotations often recited by those who favor going by established custom}. Shvut Yaacov however, does admit that one should use option 1 mentioned above, if option 2 is not available.
Chakham Tzvi in siman 161, starting with the words, Tshuva B'ol held the opposite. He held that one is obligated even at great expense to prefer option 1, and it is forbidden for one to make a blessing over the Hadassim that have the status of "Shotim" that come from Italy. He contended that the Poskim, Mahara'i and Maharik ruled leniently regarding the poor quality Hadassim only when kosher, option 1, Hadassim {mentioned above} are not available.
The accepted Halachic ruling about this dispute is decided in Mishna Brura , siman 648, siman katan 65:
Regarding the matter of Hadassim, if it is known that they are hybrids one should not use them for they are invalid and they have the same {invalid} status as hybrid Etrogs {citron fruits}. However, when nothing is known about their origin it is implied by the Achronim that we should not be afraid about this {that they are hybrids} for typical Hadassim are not the product of interbreeding (see Pri Megadim, siman 649, point 11) And that which the Shvut Yaacov wanted to do, namely, to invalidate those Hadassim that grew in the gardens of the government officials, because of a fear that they are hybrids, Chakham Tzvi and Hapanim Me'erot argued against his {Shvut Yaacov's) opinion and see in B'churay Yaacov, that he wrote that indeed the custom has spread, to view them as kosher {namely, option 1 Hadassim, mentioned above}.
One should emphasize that even Shvut Yaacov established that it is preferable to use Hadassim without a tradition if there aren't any others available. Therefore, when we don't have in our hands a Tekhelet passed down from tradition, there is an obligation even according to Shvut Yaacov to make use of the Tekhelet without a tradition, out of a doubt that perhaps we are indeed fulfilling the mitzva.
One should raise the question, perhaps we should not compare the law regarding Tekhelet to the laws relating to Hadassim with a possibility that they were interbred. Perhaps one should compare the law of Tekhelet to the laws regarding an Etrog that we have a suspicion that it might be a hybrid?
One should respond that even for an Etrog there is room to make use of it without a tradition {that it comes from a kosher source} as Be'ur Halacha, siman 648 starting with the word, She'domeh, explained:
See the Mishna Brura, what we wrote on the matter of Etrogs that are hybrids and this is a quote of B'churay Yaacov, 'it is obvious that the Etrogs that grow by us in the country of Ashkenaz {Germany} in the gardens of the government officials are all hybrids. However, those that come from Italy and there is a doubt whether they are hybrids will seemingly be kosher if we can not determine {in what manner they were produced} for we will go after the majority and the majority of Etrogs in the world, it is well known that they are not hybrids. However, for a final legal ruling we have to further investigate the matter. And in any case when there is a doubt if it was a hybrid and he has no alternative {Etrog} he should take it but without reciting a blessing", end of quote of B'churay Yaacov'. Now in my humble opinion it is possible to say that for this reason, several Poskim relied on signs {or properties of an Etrog, that we are seeking to validate} even though these signs aren't that much of a proof as the latter Poskim have written, because when combined with the fact that there is a majority { which are not produced from interbreeding} the result is that we can not protest against someone who relies upon this and recites a blessing; so this appears to me in my {namely, the author of Be'ur Halacha and Mishna Brura, the Chafetz Chaim's} humble opinion".
And so too did he write there in Mishna Brura : "see in Be'ur Halacha what we wrote in the name of B'churay Yaacov, and as it is explained there, it appears that if someone had gone ahead and already bought an Etrog or one has no place that is known where it is possible to acquire those {Etrogs} that have a legal presumption of definitely not being hybrids, in such a situation one can rely on the two external signs of the Etrog {that somewhat testify that it is not a hybrid} and recite a blessing, as I have written above".
For the sake of clarification, the Mishna Brura does indeed invalidate an Etrog that is a hybrid: "for it is not called an Etrog at all" (see Mishna Brura, siman 648, section 21). Therefore one should not contend that just when there is a suspicion of an invalid characteristic within a species that is known to us that the species is Kosher, do we say that we do not demand a tradition.
Now the fact that we are careful today to take only Etrogs that have a tradition {of being from a kosher source} is not a proof that the law is not in accordance with the words of the Be'ur Halacha, for also the Be'ur Halacha established that regarding an etrog (but not regarding Hadassim that we have a doubt if they are hybrids) that in order to recite a blessing with the approval of all the Poskim we need an Etrog that has a tradition {of being from a kosher source}. Furthermore, Rabbi Eliyahu Veissfish in his book, Arbaat Haminim Hashalem page 208, wrote regarding the ruling of the Chafetz Chaim: "In our times it requires further investigation of the matter, for in light of the great development in the science of agronomy and our knowledge of how to interbreed, it is known today of methods and possibilities to interbreed two species of fruit trees without causing essential changes in the shape or the characteristics of the fruit. According to this, the typical Etrog that is present throughout the world, doesn't have a status of having a tradition of being kosher. Neither does their external or internal resemblance to an Etrog, serve as clear proof that it is not a hybrid".
One should also take note that in the opinion of Chatam Sofer [as brought by the Mishna Brura in siman 648] "for all practical purposes one can not rely on signs (of the etrog) to be lenient and the status of Etrogs is like the status of kosher species of birds which are only eaten if we have a tradition (that the species is indeed kosher).
On the other hand, the Chatam Sofer does hold that fish that have the proper signs can be deemed as kosher for eating, even when we don't have a tradition that the species is kosher.
Rabbi Shabtei Rappaport wrote at length why one should compare the law of Tekhelet to the law of fish and not to the law regarding birds. But I will admit that his innovation depends on how you define Tekhelet according to Torah law.
In any case, it is difficult for me to believe that the Chatam Sofer would have held back the renewal of the light mitzva of Tekhelet after he ruled in siman 236 of his writings that it is possible to renew the Passover Sacrifice in our days, which is a heavier mitzva [ this is the concept known as Kal-Vachomer for those adept in the ways of the Talmud ].
R. Dov Shtein offered another argument on behalf of the viewpoint that tradition does not always establish the Halacha. He said that the fact that we rely on ancient handwritten manuscripts of the Rambam and Tur etc. in contrast to the version of the text that we have in our hands (because what is in our hands has been censored, etc.) proves that we can prove points of Halacha not based on tradition.
Therefore if some of our Rabbis established that the Purpur (or Purpura) shellfish is the Chilazon (such as the authors of Chavot Yair and Shiltei Giborim as discussed at the beginning of this article) the matter is similar to an ancient handwritten manuscript that we found from a period before censorship took place. But perhaps one might wish to push away this proof by stating that until we have a source from the time that Tekhelet was still produced, that calls the Chilazon by the name of the Purpur fish, the proofs on behalf of the Chilazon are not equivalent to the revelation of a new ancient handwritten manuscript from a period before censorship took place.
One should also add that on the subject of tradition, in the responsa, Meishiv Davar, part 2, siman 22 with the word "Ivra", we see that there are exceptions to the rule that we should not add birds to the list of kosher species without a tradition. There he informs us that initially there were many who raised an objection when Turkey was imported from a distant land to Jewish communities, for the bird lacked a tradition of being kosher. He states that even today there are those who are strict and do not make use of this bird. Nevertheless, the Jewish communities are now accustomed to permit this bird and no one opens his mouth to object and this is because it now already has a presumption of being permitted and there is no proof to forbid these birds. And so too, did the author of Meishiv Davar lean to permit a certain species of large geese that also had no tradition.
Now here was an innovation to permit a matter, that is optional for use. If so, for the matter of a mitzva, is it fitting that all of a sudden we will be more stringent than we are for Turkey?
Now one should not contend that also the Chatam Sofer who demanded a tradition to classify species of birds as kosher, would allow the eating of Turkey for in the responsa of Chatam Sofer, part 1 (O.C.) siman 127 he writes explicitly, that the "Perlheihener" although it has signs of being kosher is not to be eaten because it lacks a tradition. Now in the responsa of Melamed Laho'il part 2 (Y.D.) siman 15 we learn that "Perlheihener" is Turkey.
[Now if one has a doubt whether it really is permitted to eat Turkey {"Indik","Perlheihener"} see the responsa of Igrote Moshe, Y.D.4 siman 12. the words starting with "Hiney Inyan", where Rabbi Moshe Feinstein allowed a certain person who asked him, to eat Turkey on the American holiday of Thanksgiving.]