The injured employee, a resident of Massachusetts, was regularly employed there under written contract in the laboratories of the Dewey & Almy Chemical Company as a chemical engineer and research chemist. The employee was sent to a branch factory in California, to act temporarily as a technical adviser in the effort to improve the quality of one of the employer's products manufactured there. The employee instituted the present proceeding before P for the award of compensation under the California Act for injuries received in the course of his employment in that state. P directed D to pay the compensation prescribed by the California Act, including the amounts of lien claims filed in the proceeding for medical, hospital, and nursing services and certain further amounts necessary for such services in the future. D filed its petition in the California District Court of Appeal to set aside an award of compensation to the employee. D claimed that the employee was regularly employed at the head office of the corporation in Massachusetts and was temporarily in California on the business of the employer when injured there, and was subject to the workmen's compensation law of Massachusetts and that P, in applying the California Act and in refusing to recognize the Massachusetts statute as a defense, had denied to the latter the full faith and credit to which it was entitled under Article IV, § 1 of the Constitution. By the applicable Massachusetts statute, an employee of a person insured under the Act, as was the employer in this case, is deemed to waive his 'right of action at common law or under the law of any other jurisdiction' to recover for personal injuries unless he shall have given appropriate notice to the employer in writing that he elects to retain such rights. Section 26 directs that without the notice his right to recover be restricted to the compensation provided by the Act for injuries received in the course of his employment, 'whether within or without the commonwealth.' Sections 6, 9, and 29 of the California Workmen's Compensation, Insurance and Safety Act, Cal. Gen. Laws (Deering 1931) Act 4749, provide for compensation from insurance procured by the employer, in prescribed amounts, for injuries received by his employees in the course of their employment without regard to negligence and for the costs of medical attendance occasioned by the injuries. Section 27 (a) provides that 'No contract, rule, or regulation shall exempt the employer from liability for the compensation fixed by this act.' And § 58 provides that the commission shall have jurisdiction over claims for compensation for injuries suffered outside the state when the employee's contract of hire was entered into within the state. Both statutes are compensation acts, substituted for the common law remedy for negligence. The California Act is compulsory. § 6 (a). The Massachusetts Act is similarly effective unless the employee gives notice not to be bound by it, which in this case he did not do. § 24. The District Court of Appeal denied the petition and that denial was affirmed by the Supreme Court of California. The courts in California declared a violation of public policy if the Massachusetts act were to be enforced in California. The Supreme Court granted certiorari.