On Parshas Ki Sisa I spoke about the issur of "lo sishchat al chametz dam zivchi", you are not allowed to shechet the Korbon Pesach while owning chametz. There are 2 pesukim for this, one in Ki Sisa and one in Mishpatim.
The achronim have the following chakirah. Is this a halacha in korbon Pesach or a halacha in hilchos chametz. In other words do we say that one of the requirements of korbon Pesach is that you can't own chametz while shechting the korbon. Or do we say that part of the mitzvah of getting rid of your chametz includes getting rid of it during the time the korbon can be shechted.
The Ramban in Mishpatim seems to hold like the first tzad. The Chinuch (Mitzvah 89) sounds like the second tzad.
Rashi in Pesachim 63a also sounds like the second tzad.
A few nafka mina:
1) Who is oveir on the issur-the shochet and zoreik or even a person in the chaburah who owns the chometz evn if he is not shechting. Tosafos (Pesachim 63) and thee Ramban both say only the shochet is chayav. This is like the first tzad that it is a din in bringing the korbon. The Rambam and others say the person in the chaburah who has are chametz is chayav. This is like the 2nd tzad that it is a din in getting rid of your chametz.
2) Is the korbon still valid. Tosafos writes it is still valis cause no specific pasuk to say it is pasul. Lifi the tzad of chametz-why do I need a reason. It is pashut the korbon is kosher since it's not a chisaron in the korbon. Only if you hold the first tzad do you need a reason, otherwise you would say the korbon is pasul.
3) The Minchas Chinuch has a shaylah if this issur would apply after Pesach. L'mashel if you leave over the eimurim to burn after Pesach, can you own chametz b'hetter. L'chorah his question only makes sense if it is a din in the korbon. If it is a din in removing your chametz, after Pesach there is no issur so why would I have to remove my chametz.
4)The Tzlach writes that we don't say aseh of korbon Pesach is docheh the lav of lo sishchat because the aseh and lav are intrinsically linked. Rabbi Akiva Eiger in Mishnayos Chagiga (1:1) argues and compares it to mitzvah of re'iyas habayis with korbon. (Ayin sham). I saw that some point out this machlokes can depend on our chakirah. If the lav is a din in the korbon, then the Tzlach is correct and the aseh and lav are intrinsically linked. But if lav is din in chametz then they are separate-lav is hilchos chametz and aseh is hilchos korbon.