If any one saith, that the man who is justified and how perfect soever, is not bound to observe the commandments of God and of the Church, but only to believe; as if indeed the Gospel were a bare and absolute promise of eternal life, without the condition of observing the commandments; let him be anathema.
Again (as was also said in Canon 19), contrary to the error of some Protestants the Catholic is obliged to obey God, because (as is said in the present canon) the promises of the gospel are conditioned upon observance of the commandments: we can’t live just however we want as believers in Christ. We are not free to do whatever we wish. We must live lives of obedience to our Lord: “If you love me, keep my commandments” (John 14:15).
As usual, there is nothing here contrary to the Catholic gospel of justification by grace alone.