What does "Va'ya'asehah ka'Mishpat" mean?
Rashi: He brought the Olah in accordance with the Din of an Olas Nedavah, as prescribed at the beginning of Vayikra. 1
Seforno: He brought the people's Olah like the Halachah requires - Bnei Aharon sprinkled the blood, arranged the pieces on the Mizbe'ach and burned them.
Rashi (1:4, from Sifra) writes that "Al Rosh ha'Olah" teaches about Semichah for Olas Tzon and Olas Chovah. We can learn from both of these from here - "ka'Mishpat", i.e. also Olas Chovah requires Semichah (Beitzah 20a), and this applies also to the lamb (Tzon)!
Refer to 1:4:154:1.
Rashi writes that "ka'Mishpat", is like the law of Olas Nedavah, i.e. it requires Semichah (Beitzah 20a). A Mishnah teaches that the only Korbanos Tzibur that require Semichah are Par Yom Kipur and Par Helam Davar!
Moshav Zekenim: Even though Yisrael brought it, they brought it only for Aharon. It is like the Korban Yachid of a Nazir, which requires Semichah.
Rashi writes that "ka'Mishpat", is like the law of Olas Nedavah. Why doesn't he say that it is like the Olah above in this Parshah?
Riva: Olas Nedavah applies for all generations. The Olah above in this Parshah applied only at this time.