Why did conflict arise in 1848 in western territories over the issue of slavery?

its either

- the senate passed a fugitive law banning slavery in states where it was currently leagal

OR

- The lagality of slavery had to be decided in lands added from the Mexican Cession.

OR

- Northern congressmen wanted California to entehr the Union as a Free State....

SO SOMEONE PLEASE HELP ME FIND THE ANSWER... IT HAS TO BE ONE OF THESE...