A layout-legalizing system modifies a portion of a circuit layout that is selected by a user to generate a modified portion that satisfies a set of technology constraints and a set of design constraints. The system receives as input the set of technology constraints which a semiconductor manufacturing foundry requires the circuit layout to satisfy for manufacturability purposes. The system also receives a set of design constraints from the user which restricts how objects in the portion of the circuit layout can be modified to satisfy the set of technology constraints. The system can further receive a selection input from the user which identifies the portion of the circuit layout which is to be legalized. The system then modifies the identified portion of the circuit layout to obtain a modified portion which satisfies the set of design constraints and at least a subset of the set of technology constraints.