Laws, like sausages, cease to inspire respect in proportion as we know how they are made (Gesetze sind wie Würste, man sollte besser nicht dabei sein, wenn sie gemacht werden).
Source, in full
Though similar remarks are often attributed to Bismarck, this is the earliest known quote regarding laws and sausages, and is attributed to John Godfrey Saxe University Chronicle. University of Michigan (27 March 1869) books.google and "Quote... Misquote" by Fred R. Shapiro in The New York Times (21 July 2008); according to Shapiro's research, such remarks only began to be attributed to Bismarck in the 1930s.
Notes from Wikiquote
If you like laws and sausages, you should never watch either one being made. | Laws are like sausages — it is best not to see them being made. | Laws are like sausages. It is better not to see them being made. | Laws are like sausages. You should never see them made. | Laws are like sausages. You should never watch them being made. | Law and sausage are two things you do not want to see being made. | No one should see how laws or sausages are made. | To retain respect for sausages and laws, one must not watch them in the making. | The making of laws like the making of sausages, is not a pretty sight. | Je weniger die Leute darüber wissen, wie Würste und Gesetze gemacht werden, desto besser schlafen sie nachts. | The less the people know about how sausages and laws are made, the better they'll sleep at night. | No citation exists for where this German phrase or this translation originated. | Attributed to "Old Mr. Hawes" a member of the Illinois legislature, in "The Nation's Capital" — a banquet speech by John W. Ross (9 October 1896) in Proceedings of the Seventh Annual Convention of the National Association of Life Underwriters (1896) p. 133 - 134. This is the earliest published occurrence yet found of a statement regarding the similarity of laws and sausages, such as are most commonly attributed to Bismarck, as early as 1958, but also sometimes to Winston Churchill, Benjamin Disraeli, Clarence Darrow and Mark Twain. There are many variants that have been published in print or on the internet, but as yet no clear citations as to when or where any figure other than "Old Mr. Hawes" declared it, some time prior to 1896. -->
Variants
often attributed to Bismarck