This one is impossible to answer, since the laws and rules of implementation are so different.
In my case, I did it for many years, before the format at the landfill site changed, making it easy for management and attendants to enforce the "no scavenging rules/laws. However...
I did what I did in an effort to help Bicycles for Humanity. My charitable work was recognized by landfill site management and workers, alike. At first, I was unofficially allowed, in fact encouraged, to collect bike stuff. Today, I am a welcomed at the landfill site, coming and going as I please, provided that I do what I said I would do.
So, why not do what I do - start helping to clean up the planet, while helping people in great need at the same time - start a Bicycles for Humanity chapter in your area. It is easy to do if you are sincere in doing it.
Find a church, or something like that, who sees the value in such an operation. Get them interested in making up a shipment of bicycles for Africa. Present the interest/intent to the landfill site management and see what happens. You might get a flat no, or you might find that you will have to jump through a few hoops to make it happen.
At the moment, in my area, at least half a dozen landfill sites turn a blind eye to the salvaging/scavenging efforts of Bicycles for Humanity volunteers. One smaller town has even approached their city council seeking official and legal opportunity to salvage bicycle stuff.
Is it a lot of work - you bet! Is it rewarding - you bet, and on several levels!
Google Bicycles for Humanity and see what you get. You will be amazed at how small groups of people can make such a big difference in the lives of others, while cleaning up our collective nest.
__________________
"98% of the bikes I buy are projects".