More than 130 Labour MPs have written to the pharmacy chain after it missed its own deadline to lower the price of emergency contraception.
The age restrictions on buying the morning-after pill will be lifted following new licensing rules.
There is concern at the plans to allow teens to stockpile birth control.
Cashiers will check customers' IDs.
The ruling, which removes age restrictions for emergency contraception like Plan B, came from U.S. District Judge Edward Korman in Brooklyn, New York.
Now that Obama's been reelected, some see an opportunity to make emergency contraception over-the-counter for everyone.