Season 6 generally

Question: How does Chris still have his powers when he travels to the past, but the witches did not when they went to the past?

Chosen answer: With Chris being from the future (and being half-witch, half-whitelighter), he must know about the fact that his aunts can't use their powers in the past. Therefore, he would think to write an advanced spell so that his powers can be used.


Answer: It was a different spell, you can see that from episode Chris-crossed, the charmed ones did not drew anything when travelled to their past. It's also explained from the conversation from Phoenix and Chris.