рыба гниет с головы

The fish always stinks from the head downwards. (The freshness of a dead fish can be judged from the condition of its head. Thus, it means that if something is wrong with some country, organization, company, etc) the reason for it is that "the head" (i.e. management, government, etc.) is rotten (bad, corrupt), and all the rest is just the result of it.) — рыба гниет с головы

The guilt of criminality attaches to those responsible. ‘Well,’ said the Aga Khan, ‘fish goes rotten by the head.’ (1915 W. S. Churchill)

‘The fish’, as the saying goes, ‘always stinks from the head downwards.’ Last Sunday we deplored Mr. Michael Foot's liking for the street politics of marches and ‘demos’. Since then, a hundred Labour MPs have followed their leader's example. (1981 Sunday Telegraph 3 May 16)

Cardinal Law has to go. The Vatican has to speak up. This fish, as they say, rots from the head.(2002 Washington Post 19 Mar. A21)

Origin
Gr. ἰχθὺς ἐκ ṯῇς κɛϕαλῇς ὄζɛίν ἄρχɛṯαί, a fish begins to stink from the head. (Answers.com)