Edit for below (“too many responses”):
Irrelevant; as ClearPlay does not properly speaking edit the video; but messes with the playback timeline.
Editing the video is illegal. Messing with the timeline as the unedited film is playing? Completely permitted for accessibility, organization, and other reasons. In particular, that amazing thing called an ad blocker. Skipping 30 seconds ahead to avoid an ad is legal, but editing the ad out is not.