Actually, I believe this is false. It is my understanding that it is illegal to copy a patented invention even for your own non-commercial use.
> Most of the Member States provide the private and/or non-commercial use exception under their statutes. Only the response from Australia informed that the exception was not included in its statutes, but provided by common law as a “non-commercial use defense”
...
> Most of the Member States, however, provide a broad definition of the scope of the patent rights which encompasses all kinds of activities, and explicitly stipulate that private use for non-commercial purposes or private and non-commercial use is an exception to the exclusive patent rights. In formulating the exception, provisions of many national laws stipulate that the it applies to acts carried out in the private sphere and for non-commercial purposes or to use of a patented invention for personal needs with no purpose to make profits. The response from the United Kingdom stated that the exclusion is provided for acts done “privately and for the purposes which are not commercial”.
[1] http://www.wipo.int/edocs/mdocs/patent_policy/en/scp_20/scp_...
By what I know of it, producing a patented invention for your own purposes, outside the stream of commerce, is neither crime nor tort at common law, as no one has been provably harmed by it. As a potential juror, I do not find the "lost sale" theory of harm to be credible from any vendor operating a monopoly, state-protected or otherwise.
One presumes that, according to microeconomic theory, the monopolist restricts its supply to increase sale prices, and that it is able to sell as much as it is willing to produce at that price. If it wished to sell one more, it would have produced one more, and also lowered the sale price by a marginal amount. Since it did not, it is clear that the monopolist was not harmed by being unable to sell to the infringer, because the monopolist never intended to sell that many goods in the first place.
Nevertheless, many judges in the U.S. are far more willing to nail you to the wall with statutory law on dubious grounds before allowing you to argue anything from common law.
(a) Except as otherwise provided in this title [35 USCS Sects. 1 et seq.], whoever without authority makes, uses or sells any patented invention, within the United States during the term of the patent therefor, infringes the patent.
But, as a practical matter, companies don't go after hobbyists printing up something in their basement of course. Both because it's prohibitively expensive versus the expected monetary recovery and it's hard to find someone doing this if they're just doing it in their basement for fun.
relevant HN comment on the same issue from almost 8 years ago.
[1] https://en.wikipedia.org/wiki/Research_exemption#Common_law_...
The court did not reject the defense, but left only a "very
narrow and strictly limited experimental use defense" for
"amusement, to satisfy idle curiosity, or for strictly
philosophical inquiry." The court also precludes the
defense where, regardless of profit motive, the research
was done "in furtherance of the alleged infringer’s
legitimate business." In the case of a research university
like Duke University, the court held that the alleged use
was in furtherance of its legitimate business, and thus
the defense was inapplicable.