im sure the empire respected the power and influence of ganglords and thus their autonomy. vader even acknowledges the empire's cooperation, even though they exist outside the empire's jurisdiction, and helps them as we see when he turns over han solo to boba fett.
so the real question would be: would the empire have dared to cross the hutts?
answer imho: no. there would be nothing to gain and very useful hired hands to lose. there would be nothing at all to gain.