From the Wyoming Game & Fish Department website;
ARTICLE 4 - GUIDES AND OUTFITTERS
23-2-401.Guides required; exceptions; issuance of resident guide license.
(a) No nonresident shall hunt big or trophy game animals on any designated wilderness area, as defined by federal or state law, in this state unless accompanied by a licensed professional guide or a resident guide. There shall be at least one (1) licensed professional guide or resident guide accompanying each two (2) nonresident hunters. The commission may also specify other areas of the state, or specific big or trophy game species, for which a licensed professional or resident guide is required for nonresidents, for purposes of proper game management, protection of hunter welfare and safety, or better enforcement of game and fish laws. The commission may allow licensed guides to accompany more than two (2) hunters but no more than six (6) hunters in specific areas.