Why is it illegal to use a periscope?

Using a periscope itself is not inherently illegal; however, its use can be restricted in certain contexts, such as in areas where privacy is expected or in situations involving security and surveillance laws. For example, using a periscope to spy on someone without their consent may violate privacy laws. Additionally, in military or restricted zones, using equipment like a periscope could be subject to regulations to prevent unauthorized observation. Always check local laws and regulations regarding surveillance and privacy.