Wis. Stat. § 93.08: Access for law enforcement.

In performing their duties or in enforcing the laws entrusted to their administration, the department and its authorized agents may do all of the following:

(1) Enter, within reasonable hours, any field, orchard, garden, packing ground, building, freight or express office, warehouse, car, vessel, vehicle, room, cellar, storehouse, cold storage plant, packing house, stockyard, railroad yard or any other place of business, which it may be necessary or desirable for them to enter.

(2) Open any box, carton, parcel, package or other receptacle, inspect the contents thereof, and, upon payment or tender of the market value, take samples of any product or material contained therein.

(3) Inspect products and materials and collect and test samples of them.