1. A printing system comprising: a printer configured to print an image on a first sheet; a sheet processing apparatus, the sheet processing apparatus comprising: a binding device configured to execute, at a first binding position, a binding process for the first sheet conveyed along with a conveyance path from the printer; a sheet insertion portion configured to receive a second sheet inserted by a user; and a sheet detection sensor configured to detect the second sheet which is received via the sheet insertion portion and is positioned at a second binding position, the second binding position being different from the first binding position in a width direction orthogonal to a direction of the conveyance path, wherein the binding device is configured to move toward the second binding position and execute, at the second binding position, the binding process for the second sheet based on the sheet detection sensor detecting the second sheet; one or more processors; and one or more memory devices including instructions, which when executed by the one or more processors, cause the printing system to: receive a print instruction causing the printer to print the image on the first sheet; determine, in a case where the print instruction is received, whether the second sheet is not positioned at the second binding position, wherein the determine is performed based on the detection result obtained by the sheet detection sensor; and cause the printer to print the image on the first sheet based on the print instruction in a case where it is determined that the second sheet is not positioned at the second binding position, wherein, in a case where it is determined that the second sheet is positioned at the second binding position, the printing the image on the first sheet based on the print instruction is restricted.