Can you legally show a TV ad during a speech?

Answer 1

If it's your own work, or you have a license from the owner, there shouldn't be a problem.

Otherwise, the issue of copyright infringement will depend upon the context of the speech: educational, critical, news, one-time or repeated, etc., in order to qualify for the defenses of statutory exemption or "fair use" of materials created by others. One factor in possible infringement of copyright is the amount of work that is being copied (or performed in public), especially where a snippet would be sufficient for your purposes and you show the entire work. However, even a snippet can be infringed if it contains the essence of the original work. Other factors of "fair use" weigh the economic harm to the owner and economic benefit to the infringer. For example, if you could have obtained an expensive license but chose not to, and used the entire TV ad for your own promotion and financial gain, it is unlikely to be excused and could even be "criminal".