Because the leader is also the legal representative of the organization!
Within the organization's scope of operations, a contract signed by the legal representative within their authority does not require an official seal to be effective.
Of course, this organization isn't commercially oriented, so whether the leader's signing of the contract exceeded their authority is unclear.
But Tian Junfa specifically sought legal grounds to counter the opposing evidence this time—he truly wants to win, and he truly wants to improve!
"Taking a step back, even if my client's behavior at the time exceeded their authority, according to the principle of retroactive leniency, this case should adhere to the previous 'Contract Law.' According to Article 50 of the then 'Contract Law':