Indeed, we can use Haskell lists as the amb operator and implement require as

    require :: Bool -> [()]
    require True  = return ()
    require False = []

and then express amb-like computations in effectively the same way:

    sample :: [(Int, Int)]
    sample = do
      x <- [1,2,3,4,5]
      y <- [1,2,3,4,5]
      require (x == 2 * y)
      return (x, y)

after which the value of sample is [(2,1),(4,2)]. (Also, my require is effectively the same as the guard function found in Control.Monad, specialized for lists.)