For years now it has been increasingly difficult to buy strong painkillers online. The influence of the FDA and DEA on the web is only getting stronger, and means that, with the FDA’s increasingly aggressive stance in particular, previously available medicines are being reclassified as prescription only, for example even the relatively mild opioid painkiller tramadol.
The Ryan Haight Online Pharmacy Consumer Protection Act of 2008 is the key US legislation to enforce restrictive measures against online pharmacies.
The full read of the Ryan Haight Act can be read here:
Ryan Haight Online Pharmacy Consumer Protection Act of 2008

* Since 2009, The Ryan Haight Online Pharmacy Consumer Protection Act requires internet pharmacies to display information about the businesses, pharmacists and physicians associated with the website.
* The Act prohibits the sale of prescription drugs through online pharmacies when the website refers the customer to a doctor who then prescribes medication without seeing the patient. This effectively outlaws telemedicine where scheduled medicines are involved.
* Finally, the Act provides the states with a new enforcement authority that allows the attorney general to shut down any site which violates the law.

The effect of the Ryan Haight act today is that is nearly impossible to procure strong painkillers online, as they are all prescription only. A discussion on how was the situation with online pharmacies before the Act can be read on Pharmacy Reviewer forum here:
Pharmacy Reviewer (Buying drugs back in the day)
As of now, the only two options are 1) unreliable or even dangerous email dealers possibly linked to drug cartels in Mexico. 2) So-called “dark web” marketplaces such as the various successor marketplaces to the recently closed Silk Road on the Tor network. Ordering from sources like these could lead to money loss, or even arrest, so this path is not recommended.

The FDA and DEA have effectively achieved their objective of making it almost impossible to buy strong painkillers online and making the most viable route obtaining Rx through face-to-face contact with qualified medical personnel.