The concept of private law in the common law is somewhat broader since it also encompasses private relationships between governments and individuals or other institutions. In other words, relations between governments and persons based on contract law or the unlawful act are governed by private law and are not considered to be part of public law. Coercion has been defined as a „threat of harm that is made to force a person to do something against his or her will or judgment; in particular, an unlawful threat by a person to impose a manifestation of another person`s apparent misunderstanding on a transaction without real will.  One example is in Barton v Armstrong  in a person who was threatened with death if he did not sign the contract. An innocent party wishing to cancel a contract of coercion of the person need only prove that the threat was made and that this is a reason to accede to the treaty; the burden of proof then shifts to the other party to demonstrate that the threat had no effect in getting the party to conclude the contract. There can also be constraints to the commodity and sometimes to an „economic constraint“. In other countries, certain sectors are excluded from the definition, in particular sectors that are effectively regulated or that are the subject of major private sector initiatives, such as. B in the field of ICTT. In some countries, agreements involving a more limited transfer of risk, such as. B management contracts are excluded from the definition for institutional reasons, as the authorities prefer that they be covered by traditional procedures for the purchase of goods and services. You will find exemplary laws under PPP legislation and laws. Contract law is based on the principle expressed in the Latin phrase pacta sunt servanda („Agreements must be respected“).
 The Common Law of Contract arose from the meantime defuct writ of assumpsit, which was originally an unlawful act based on trust.  Contract law is covered by the ordinary law of obligations, together with the unlawful act, abusive enrichment and reimbursement.  There is no universally accepted definition of public-private partnerships (PPPs). The PPP Knowledge Lab defines a PPP as „a long-term contract between a private party and a public body for the provision of a public asset or public service, in which the private party assumes significant risk and management responsibility and the remuneration is linked to performance“. As a general rule, PPPs do not include service contracts or turnkey works contracts, classified as public procurement projects, or the privatisation of public service enterprises for which the role of the public sector is limited. For details, see PPP Knowledge Lab. More and more countries were creating a definition of PPPs in their laws, with each country adapting the definition to its institutional and legal specificities. In both the European Union and the United States, however, the need to prevent discrimination has undermined the full level of freedom of contract. Legislation on equality, equal pay, racial discrimination, discrimination on the basis of disability, etc., has limited full contractual freedom.  For example, the Civil Rights Act of 1964 limited private racial discrimination against African Americans.  In the early twentieth century, the United States experienced the Lochner era, where the U.S.
Supreme Court established economic rules based on freedom of contract and the consultation clause; These decisions were eventually overturned and the Supreme Court found compliance with laws and regulations that restrict freedom of contract.  The U.S. Constitution contains a contractual clause, but it has been interpreted to limit only the retroactive depreciation of contracts.  Contracts are governed primarily by state law, general (judicial) law, and private law (i.e., private agreement). Private law in principle includes contractual conditions between parties exchanging commitments. . . .