In "saving private Leo" when the Lange brothers kill Maria by stabbing her, they hold down Leo so he can watch her die. Why couldn't he orb to her? Chris could orb when paige was holding him with her pitchfork, so Leo should have been able to orb.

Which brings me to, Why does Chris have his powers in the past? The charmed ones never did. In all Halliwell's eve, Prue said that they may not have their powers because technically they didn't exist yet, so neither did their powers. Yet when Chris technically did not exist, he still had powers.