If Mexico fought a six day war against the USA & won, annexing southern Texas afterwards....?

...Then divided southern Texas up with security walls, checkpoints etc, blockaded all access, limited the amount of food allowed in, and allowed power as they saw fit.....would the residents of southern Texas be justified in lobbing old rockets at towns close to the Texs/Mexico border if those were the only weapons they had? Or even used themselves as human bombs? And would Mexico be right in blitzing Texas border towns with gunships & artillery, killing ten times as many Texans as Mexicans had died?