Here is a post from wikipedia about an attempt that was made to restore semicha in the time of the Beis Yosef. The issue is based on a Rambam in Yad Hachazaka and Pirush Hamishna, that semicha can possibly be restored by consensus of chachmei yisroel in E.Y.
Attempt by Rabbi Jacob Berab in 1538. Rabbi Berab assembled 25 of the most leading Rabbis of Israel, who at the time were located in Safed, and re-instituted the Semicha. They convened and ordained Rabbi Berab as their "Chief Rabbi". The Rabbis of Jerusalem felt a slight on their honor and declared the election invalid, and a major dispute ensued. Some Rabbis held that it wasn't possible to renew the Semicha, but Rabbi Yosef Karo, author of the Shulchan Aruch, took the position that the procedure was valid and he was one of four Rabbi ordained by Rabbi Berab. Rabbi Karo in turn ordained Rabbi Moshe Alshich who in turn ordained Rabbi Hayyim Vital the prime disciple of the Ari Hakodosh. The new Sanhedrin has modeled its actions after this attempt.
The issue is addressed at length in the kunteros at the end of teshuvos maharal ben chaviv, where he has a heated exchange with the mahari bei rav (R. Yakov beirav) who was the first to receive the semicha. The maharalbach (ben chaviv) was located in Yerushalayim and spills much ink on explaining that without his agreement, their actions were futile.
But what was the purpose in restoring semicha? There was a group of people who committed aveiros for which they deserved kareis. They desperately wanted to do teshuva and receive malkus to remove the status of kareis - for this they needed a beis din of semuchin (to carry out the malkus). The problem was that malkus requires warning and these people never received warning for their aveira, and therefore the malkus would have to be given based on their own admitting to their aveiros. Can one volunteer to receive malkus?
The MaharalBach writes that there were people who had violated issurei kareis and wanted to receive malkus, so that based on our mishna they will exempt themselves of kareis. The first question that the maharalbach addresses is whether the concept of חייבי כריתות שלקו נפטרו ידי כריתתם only applies in conjunction with teshuva. The gemara in makos 13b implies that teshuva is a necessary component, but the mishna makes no mention of it. There is even a contradiction in the Rambam. In the pirush hamishna both at the beginning and end of the perek he says teshuva is a necessary component but in Hil. Sanhedrin (17:7) he makes no mention of it. The maharal bach explains that Teshuva with malkus is necessary to remove kareis, but either teshuva or malkus can restore his status as being a kasher - כשלקה הרי הוא כאחיך.
Being that malkus really serves the function of "yesurin" which in conjunction with teshuva help to remove the kareis - it is plausible that even if the malkus is given voluntarily without actually being chayev malkus, it would remove the kareis.
This developed into a major debate between the maharalbach and the mahari beirav, whether volunteering for malkus would work to remove the kareis.The argument posed by the Mahari Beirav is that if malkus can work to remove kareis when one is warned, it should certainly be effective in the absence of warning. The rationale is that the smaller the crime, the easier it should be to remove the punishment. If the punishment of kareis can be removed from a major crime with warning, it should certainly be removed through malkus by a smaller crime (without warning). The MaharalBach adamantly disagrees for 3 reasons: 1. Warning isn't a factor for Hashem. Since he knows that the person violated intentionally, it is as if he was warned in G-d's eyes, but for technical reasons, has no ability to receive malkus to remove the kareis. 2. Beis Din is cannot whip him by his own volunteering. The Beis Din is not allowed to due anything that indicates that they are believing him based on his own admitting. 3. The Rambam (Sanhedrin 18) writes that malkus is a gezeiras hakasuv LIKE the death penalty. Just as one cannot volunteer for the death penalty, he cannot volunteer for malkus. In addition he writes that malkus itself can lead to misah, and beis din cannot take on that liability.
Furthermore, the maharalbach explains that the only type of malkus that can replace kareis is when their is severe embarrassment, by the malkus being imposed by the beis din forcefully. Any malkus that is done voluntarily doesn't have the same level of embarrassment and therefore doesn't qualify. R. Chaim Soloveitchik has a similar approach but more lomdush where he explains that the status of "malkus" is only when imposed by a beis din. He continues to be medayek in Rashi 23b to support the point that without witnesses and warning, malkus cannot be given to replace the kareis.
However, the MahariBeirav was not convinced and writes that he has already passed on his semicha to 4 Rabbonim in tzefat just in case he is exiled as a result of the controversy. One of these students is assumed to be R. Yosef Kairo. The debate between the two gedolim takes on a very strong tone - one of the strongest debates of the greatest gedolim in the history of klal yisroel.