The Sokovia Accords are legal documents created to regulate the activities of enhanced individuals and the organisations who employ them. Private organisations, like the Avengers, are either disbanded or moved to operate under the supervision of the United Nations (UN).
These documents state clearly that all unauthorised activity involving an individual with enhanced abilities--innate or acquired--is illegal
. Those who do not abide by these regulations are arrested and may be detained indefinitely without a trial, regardless of intent. Whether the enhanced individual commits crimes or obstructs them, they are considered a threat to national security and consequences are severe.
There are two primary teams assigned to enforce the Sokovia Accords: Sokovia Accords Task Force (Thunderbolts)
and the Superhuman Restraint Unit (SRU)
. More information can be found here