You want to look at customs declaration forms and the penalties for lying on them.

The consequences will vary by country although the forms themselves are very uniform in my experience.

Every single item has some tax on it, however things like your clothes and personal possessions may be excluded at the customs' official's discretion.

Lying on those forms or omitting things you are required to declare is illegal and punishable with prison.

http://www.criminaldefenselawyer.com/crime-penalties/federal...