This is a excellent blog by Doron Gladdenon on legalism.
"Remember, the Pharisees were liberal in theological beliefs and rigid in their morals. I could picture them, laying heavy burdens on men like certain “Acts 29/Missional preachers”, Word Faith preachers, Catholic Priests, and other motivational speakers do (Osteen, Meyers, and others). For example, in Driscoll’s case, it is certainly legalistic to build a philosophy of ministry geared toward “unbelievers” and then cursing at them for not acting the way you want them to act. Especially when a person cannot do what God requires until He has regenerated them. Jesus Christ said “I will build my church!” The pope is not the head, neither is any minister, but Christ alone. He rules over His church. If any man claims to rule over the church of Christ, whether implicitly or explicitly, then He is at war with Christ."
Full article here.