Basically, Minnesota law regarding drug testing protects the Pat and Kevin Williams from being punished for taking something not on the label. While it was against NFL rules as the policy of being "responsible for anything you put into your own body" protects StarCaps from any wrong-doing, Minnesota law does not.
Grant and Smith didn't get so lucky in Louisiana as the state law sides with the NFL policy, and they will be forced to sit for weeks 2-5. Why weeks 2-5? Because the ruling came after the Tuesday before the game, Grant and Smith get to play Week 1 against the Detroit Lions, but will miss New Orleans' Week 5 game against the Giants.
So not only did the Saints players get screwed, but it gets worse because instead of missing a game against a team looking to win its first game since 2007, they miss a game against a team that won the Super Bowl in 2007.
The NFL must do something about their substance-abuse policy to prevent state laws from creating a loophole so something like this doesn't happen again.
For the Vikings, it's certainly good news. Common knowledge says the Vikings season relies on the play of their defense, and the play of their defense relies on the Williams wall. If those two were to miss four games, the Vikings winning even two of them would have been a great accomplishment.
For the Saints, they're going to lose two starters on an already below-average defense and in a competitive NFC South, that could mean the difference between the playoffs, and another .500 season.