In this paper we develop bond-graph representations for ideal mechanical constraints, both embedded andadjoined, by stating and applying the principle of virtual power, at the particle level, to both types of constraints.The resulting system-level bond graph provides a bond-graphic derivation of Kane's equations for a general nonlinearnonholonomic system. Four examples are then shown to illustrate the application of the method to specific systems. Inthe final example we show how to apply the method to an existing bond graph having causal conflicts that force inertialelements into differential causality. The power and simplicity of the method, when applied in this fashion, recommendit for incorporation into standard procedures for sequential causality assignment of bond graphs.