Back in the 1970's and 1980's, the US government (and other governments throughout the world) placed restrictions on crypto because it could be used by criminals. The rationale was the following: Even though law-abiding citizens have a legitimate use of crypto, criminals and terrorists can use it to hide evidence or distribute information securely, and otherwise make it more difficult to prevent and prosecute crimes and acts of terrorism.
At first, there were some attempts to make use of crypto illegal, but that was not possible. So the US government did some other things. For example, they standardized on DES, which was a weaker algorithm (key size was limited to 64 bits), then they weakened DES (artificially reduced the key size to 56 bits). They placed export restrictions on crypto, and introduced Clipper in the hopes that the only crypto available would be a version with a government back door built in. In the end, crypto became too widely available and any attempts to restrict it became futile.
Because of my experience in the crypto industry, this idea -- because something can aid criminals it must be outlawed or severly restricted -- has always interested me.
A story in the San Jose Mercury News talks about another case. Bob Wallace of Saratoga, CA, sells a water purifying product. The product contains iodine crystals, which can be used in the production of methamphetamine. So the government, through the Drug Enforcement Agency (DEA), has demanded that Wallace pay a special regulatory fee, report suspicious customers, prove his security is sufficient, and other things. Eventually, because Wallace was not able to secure a permit to trade in iodine, his supplier stopped sending the raw materials (after the DEA threatened that company with legal action if they continued doing business with Wallace). So Wallace is out of business.
This is similar to the restrictions placed on cold medicines containing pseudoephedrine. You can't get them over the counter, and when you do buy them the pharmacy sends your your name to a registry that tracks purchases.
One thing I found interesting in the article is a quote from Barbara Carreno, a DEA spokesperson. "Methamphetamine is an insidious drug that causes enormous collateral damage. If Mr. Wallace is no longer in business he has perhaps become part of that collateral damage, for it was not a result of DEA regulations, but rather the selfish actions of criminal opportunists. Individuals that readily sacrifice human lives for money."
There is a logical flaw in there. In part one, she mentions collateral damage caused by the drug. She further claims that Mr. Wallace lost his business because of that collateral damage. However, Wallace did not lose his business because of the drug's collateral damage, rather he lost it because of the enforcement policy's collateral damage. She said "it was not a result of DEA regulations," but that's exactly why he lost his business.
There seems to be a threshold for criminal usage. For example, criminals use ski masks to hide their faces and gloves to prevent leaving fingerprints, but we don't make it hard to buy ski masks or gloves. Or accountants use bookkeeping software or books to hide embezzling. Or spray paint is used for graffiti. Or kitchen knives, baseball bats, lighter fluid, laptops, cell phones, fertilizer, apricot pits, hair dye, screwdrivers, wire cutters, cameras, and on and on are used or can be used as tools to commit crimes.
Why does the government heavily regulate some tools and not others? I think there are two reasons. The first is when drugs are involved, the government is very zealous. The second is, they can. I suspect if law enforcement agencies could place heavy handed regulations on more items that are dual use (honest and dishonest), they would.
If they can, they will. If for some reason they can't, they'll just have to figure out how to get along without the regulations. With cold medicine and iodine crystals, they can. With crypto they can't. The legitimate users of crypto have a lot of lobbying power (banks and other financial institutions especially) to make sure the government relents. There's not enough money in cold medicine and iodine crystals to afford the lobbying muscle needed to get the government to back off.