legal ground
Article 464 of the Civil Code
A contract is an agreement between civil subjects to establish, change and terminate a civil legal relationship.
Article 465
Contracts established according to law are protected by law.
A legally established contract is legally binding only on the parties, except as otherwise provided by law.
Article 490
If the parties enter into a contract in the form of a contract, the contract shall be established when the parties sign, seal or press their fingerprints. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it.
Article 502
A legally established contract shall come into force upon its establishment, except as otherwise provided by law or agreed by the parties.
In accordance with the provisions of laws and administrative regulations, if the contract should go through the approval procedures, such provisions shall prevail.