Excuse me, is it a trademark infringement to stick a trademark sticker on a tourist suitcase? Is it sanctioned by law?

Personally, it is not illegal, nor is it trademark infringement. As long as it is for your own use, it is not infringement, and the goods have not been put into the market. Paragraph 4 of Article 52 of the Trademark Law stipulates: changing a registered trademark without the consent of the trademark registrant and putting the goods with the changed trademark on the market again. This is an infringement.

If in doubt, please ask.