Oddly enough, copyright law in it's base form is fairly simple. Once something has been created in tangible form, the creator holds the copyright to the item for their lifespan plus 70 years. It does not matter what form it is in, whether recorded, digital, written, photographed, whatever. That's it in a nutshell. As for other countries not abiding by US copyright law, please read this Wikipedia entry concerning the Berne Convention which requires all signatory countries to recognize copyrights held by the citizens of all other signatory countries. https://en.wikipedia.org/wiki/Berne_Convention
This is the link to the Wikipedia entry with the list of signatory countries of the Berne Convention. https://en.wikipedia.org/wiki/List_of_parties_to_international_copyright_agreements
Oddly enough, the US did not become a signatory to the Berne Convention until 1989. Agreeing to the Berne Convention required a partial rewrite of US copyright law, including the requirement that all copyrighted material be registered. This no longer applies.
So getting back to the original topic of copyright, unless you are using something listed as public domain to make patterns from, it is safe to assume it is copyrighted and you would need permission from the copyright holder to use the image.
Oddly enough, gaining permission is fairly simple.
1. Determine who the copyright holder is
2. Contact them in a tangible form (email, snail mail, facebook, etc)
3. Introduce yourself, explain what it is you do (attach an example if able), and explain how you wish to use their work; to make patterns for sale, to make patterns to post on websites such as SSV, or for personal use only
4. Explain that cuttings will be made from the patterns (attach example if possible, preferably a cutting of the pattern example you used) and that in many cases those cuttings may be sold at craft shows, etc.
5. Ask what if any credit they would like on the pattern. Some don't care, others want their name or even website added to pattern.
6. Thank them for their time and consideration
I have had a couple of copyright holders turn me down flat, but most of the time they are happy to allow you to use their work for patterns, especially since you respected their copyright and asked first. (rare thing these days) Some have said pattern can not be sold, others have said cuttings and patterns cannot be sold. Always save all correspondence from each copyright holder as proof of the granted permission.
Hope this helps someone