The Italian-American community in A View from the Bridge is depicted as having its own rules, way of doing things, and code of honor. Like many immigrant communities, Italian-Americans in Red Hook feel somewhat apart from the rest of society, still not quite fully accepted. Adhering to a set of social rules helps to bind the community together, giving it greater strength and cohesion in the face of prejudice and discrimination.
This helps to explain why Eddie Carbone's actions in ratting out Marco and Rodolpho are so unpopular in the neighborhood. In turning the immigration authorities on to the brothers, he's violating the unwritten law of the community, undermining its sense of unity and solidarity.
The distrust that the Italian-American community has for the law can be seen in Alfieri's opening soliloquy. Alfieri is a lawyer, and as he ruefully admits, it's considered unlucky to meet a lawyer on the street. When people in the neighborhood see him pass by, they nod uneasily. In this neck of the woods, justice is regarded as very important. But it's not justice in the legal sense that Alfieri is referring to: it's the kind of street justice that leads to notorious gangsters like Frankie Yale being cut down by machine-gun fire.