A.T. Robertson Commentary Romans 11:6

"But if it is by grace, it is no more of works: otherwise grace is no more grace." — Romans 11:6 (ASV)

Otherwise (επε). Ellipse after επε (since), "since, in that case."

Is no more (ουκετ γινετα). "No longer becomes" grace, loses its character as grace. Augustine: Gratia nisi gratis sit gratia non est.