By Rich McKay and Jonathan Allen (Reuters) – A pivotal defense argument of the three white men on trial in Georgia for killing Ahmaud Arbery, a Black jogger, is that they were trying to make a citizen’s arrest under a Civil War-era law that was later repealed amid an uproar over the shooting. When the fatal encounter occurred on Feb. 23, 2020, it was legal in Georgia for people to arrest someone where they had “reasonable and probable grounds of suspicion” that the person had just committed a felony. Outcry over the killing led to lawmakers revoking the statute in May. Legal observers say pros…