Vito was a live and let live kinda guy, at least with people that were as dangerous as he was. rolleyes If Sollozzo and Tattaglia went ahead with the drug business, for the first two-three years or so Vito would shrug his shoulders and say "let them do what they want, I don't control them".

As Vito discovered the amount of money that they were making and the fact that even some of his contacts could be swayed by Sollozzo-Tattaglia-Barzini I think he would call Tom/Sonny in and without admitting any lapse in judgment, give them permission to quietly get into the trade, behind the scenes and all that. In the interim Clemenza and Tessio would also have been dealing with complaints from the rank and file and passing those up to Vito.

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.