Wyoming constitution
Article 19: miscellaneous
Section 7

It shall be unlawful for any person, company or corporation, to require of its servants or employes as a condition of their employment, or otherwise, any contract or agreement whereby such person, company or corporation shall be released or discharged from liability or responsibility, on account of personal injuries received by such servants or employes, while in the service of such person, company or corporation, by reason of the negligence of such person, company or corporation, or the agents or employes thereof, and such contracts shall be absolutely null and void.