I bought several items from the DW and some of the packages were seized by customs because Switzerland is not part of the EU and customs takes its job seriously. Also, those products aren't available domestically so I had to order them from abroad (for personal use).
There are two kind of procedures:
1. Products that can be identified as medical products: Such as benzos in original blisters. Customs will send you a letter "We found a suspicious parcel here, we will hold it back for further investigations.". Later, you'll get a letter from the "State department of drugs" (can't really translate it, it's the state agency which is responsible for all the pharmaceutical products) [Edit: For the Swiss-Germans: "Kantonsapothekeramt"] and they will send you a letter "It seems you ordered some illegal products, please explain yourself, blah blah."
So I just sent them an email "Yeah, I ordered that for personal use, I thought the website was legit." and they responded "Ok, but don't do it again." And I had to pay a fine of about $400 (still cheaper than moving to Belize).
2. Products customs can't identify: Which means any drugs or medical products not in blisters. Customs won't send you a notice. It goes straight to your local LE. They will send you a letter with a date when you should show up for questioning. You can use this time to clean your house (or move to Belize) or don't do care at all, like me.
I showed up for the questioning. Yes, could have lawyer up, but paying a lawyer and missing working hours for being in court would still be more expensive. So I showed up for the questioning. "Do you know anything about this letter customs found?" - "Yes, I ordered it." - "Ok, we'll get a search warrant right now and search your house." So they went to my house, searched it (half-assed) and found some XTC pills which I told them about before. Which doesn't matter, charges would be the same.
So again, had to pay few hundred bucks, thing was closed.
Now, since both of the two scenarios happened to me several times I finally got a criminal record regarding drugs. And I'm on "probation" now, which means if they catch me again I'll have to pay about $3,000 on fines.
Regardless, I now work for the government. They did the background checks and concluded that drug charges aren't anything to worry about so I got the job.
Conclusion: Small buyer in Europe, stay calm. They don't care about personal buyers and even if they to, you have at most to pay a fine and you'll be fine.
Your criminal justice system is much different than the USA. One arrest here basically means that you're never going to have a good job again plus, you're going to do jail time.