It is the Law. These people were protesting against a law, voted for by Parliament with an overwhelming majority.
Apparently as they consider themselves to be above the law, one hopes they are prepared to accept the consequences.
However , as it is Lord Hermer, a Human rights lawyer who was speedily ennobled to enter the House of Lords and be appointed, unelected and with no previous Parliamentary experience, as Attorney General, to decide whether or not to prosecute hundreds of protesters arrested for supporting Palestine Action, it is difficult to have faith in his probity.