Repeated Milgram's baseline study and measured participants to see if they were internal or external locus of control. 37% internal and 23% external did not continue to highest shock level. suggests locus of control can be a valid reason for disobedience.
Twenge et al (2004) - contradictory evidence for LOC
Meta analysis - analysed data from American locus of control studies, conducted over a 40 year period. Data showed over this life span, people became more resistant to obedience but also became ore external which is not expected, so suggest it is not a completely valid reason and may only tell us about resistance in new situations.